Well, the second PH for 4E is out, and per the Rule Of Threes it posits a new, third force involved in the deity/primordial conflict: primal spirits of the material plane, who finally get fed up with the fighting and banish the remaining gods and primordial from their territory. Four PC classes - the Barbarian, Druid, Shaman, and Warden - derive their powers from these Material plane spirits. The other classes added are Avenger (divine), Invoker (divine, apparently the Favored Soul under a new name), Sorceror (arcane), and Bard (arcane). Polymorphing and summoning are back, but in a highly minimalized fashion - when you change form, you keep your normal game stats and gain a new movement rate or mode, and possibly a new attack mode depending on form (i.e. become a wolf and you get to bite opponents). Summoning is similarly handled in a bare-bones manner. Easier to play, I suppose, but...
4E Player's Handbook II and new "Primal" material
Some of my thoughts about the new classes:
I feel that most importantly an Athar Divine character is going to be an Invoker. After all there isn't much need for clerics anymore, as any leader class can heal and anyone with Ritual Casting and ranks in religion or heal can do advanced healing. I definitely see "wielding the power the Gods use" as something a bunch of Athar would do, they'd call that power they wield the Great Beyond and would be Invokers.
Mercykiller/Sodkiller/Sons of Mercy Avengers, that could be a scary idea. Their powers make them very relentless against their quarry.
It's good to see bards back, they're more like 2e bards than 3e bards now. And they are an excellent class again for Tieflings (rogues not so much anymore).
Druids are at least more flexible in what they wild shape into. They can look like anything the player says they look like. It makes me want to make a "Blight Druid" that's been touched by the Far Realms and wild shapes into a mass of tentacles, clawed pseudopods and wings.
Of course for that matter a Shaman doesn't need to have it's spirit companion look like any particular animal. A Mechanus Shaman is probably going to have a ghostly mechanical creature or something like a Moigno for a spirit companion. Much like how a Limbo Shaman has an amorphous shape-shifting blob as a spirit companion.
As for the new races:
I'd of course say the eternally reincarnating Deva is just one variety of Aasimar. And that some Aasimar of the "Deva" bloodline actually have a racial memory of past ancestors, much like how the Bene Gesserit can draw from the Other Memories.
Shifters, not only would I say there's a lot of them living in the Beastlands, but that some of them feel that they're descendents of the Guardinals rather than Lycanthropes. Though I'd also say that some shifters can become Guardinals much like how Eladrin PCs can become Shieres now.
I'll talk more about everything later but I wanted to mention that I'd put the Invoker closer to the Archivist (Heroes of Horror, I believe) than the Favored Soul.
It's interesting that 4e now has two contradictory origins for the rakshasa. The Manual of the Planes says they're the descendants of arcanaloths, while Player's Handbook II says they're devas who have fallen into evil in their previous incarnations. The latter explanation might be a little more interesting (and fits with the Hindu background of the creatures), but makes them utterly solitary; each rakshasa is created on its own, with its own unique reason for its fall from grace, with no reason to ever have contact with others of its kind other than the common experience of once having been a deva. Oh, perhaps a few of them knew each other in their former state, but there's no reason for a rakshasa society, no caste system or order of knights (despite the existence of rakshasa knights in the Monster Manual), no maharajas or rakshasa king.
The arcanaloth origin kind of makes sense, since arcanaloths were always supposed to be able to reproduce sexually; I kind of like the idea that their descendants, after too many generations away from the fiendish planes, are no longer true 'loths, but something else.
Of course, there's also the traditional Hindu explanations, having them created as guardians of the primordial waters or born from the wrath of Shiva or descendants of an ancient human sage.
Probably best to leave it somewhat ambiguous. I still like them as natives of Acheron, as Planes of Law said, though that doesn't necessarily contradict the other explanations. All of them are better than the 3e "crossbreeds of devils and fiendish animals" idea from Dragon Magazine.
It's not contradictory - the PH2 states that evil Devas MAY become Rakshasas in their next incarnation, not that ALL Rakshasas are fallen former Devas! An important distinction... MOST Rakshasas have always been such, as per the MM and MOTP (MM states they are related to demons, while MOTP futher specifies that those demons were Arcanaloths, what with 'Loths being classed as demons in the current rules.) Hmm... given that Devas automatically reincarnate, can they be raised from the dead? Presumably there is a time lapse between incarnations to allow PCs to bring back their dead Devas, since otherwise they'd end up playing a new incarnation with no memories of what he/she was doing prior to their death! Plus said Deva would have to level up in a PC class all over again, and would have none of his/her former equipment! (Said levels obviously do not carry over between lives; otherwise Devas would be phenominally powerful beings maxed out in all PC abilities, and only suitable as NPCs!)
(Oh, and I neglected to mention that the MONK class is NOT in the PH2! Neither are any Psionic classes... I guess they'll be in PH3, or perhaps the Monk will turn up in a new Oriental Adventures...?)
The Monk playtest is due out next month, coming from PHB3 since the only places that have new classes now are the Player's Handbooks and Player Guides to Campaign Setting (Swordmage for FR, Artificer for Eberron). You'll probably need to be on insider to look at the Monk, much like how the Barbarian and Bard were.
As far as the whole Deva and Rakshasa thing, I think it's possible that there may have been a whole group of Devas that fell at the same time. Even though I'd only have that as a possibility on what Rakshasa are, and still leave their origins varied. Of course I'd feel that you'd definitely have to factor in a Power such as Ravana into the influence of the Rakshasa, and how their society is structured.
You should also read my musings on the different power sources in Planescape (Shameless Plug). I have my own explanations on what primal and spirits are.