This all has me torn regally. On one hand I would have liked to see only war as source book for DH, I certainly can see a lot of cross over. On the other hand, a huge IG fan I'm glad they are getting full scale love, rather than what they could fit in source book. If it can down to a decision to cut 400 pages of material writen by rabid games designers or to whack on 200 hundred pages of how to play and release it as a core book, I think they made the right descision.
For the Eldar, I hope it's not down to some GW fiat. I'm sure there's plenty of good reasons not too at the moment but I would like to see that eventually. Eldar re the best, most rounded Xeno's species GW have. They've come a long way from their Space Elf roots... well, in design aesthetic and background if not in character.
Love Orks too, there a perfect counter point to all other species. There's a suprising amount of background out there for them and they have a bunch of unique RP options. If a whole game is too risky I'd love to see a Black Crusade supplement to add Ork freeboota characters (or Chaos Orks, there I said it..) or run the whole thing as an Ork game. They've got all the same bases covered as a normal group an easy 6 clan but many tribes (or 7 if you include freeboota) system for character gen.
Maybe they could release Eldar as a source book for RT, concentrate of a corsair crew if life within a Craftworld is too difficult. Seems a bit weird to have an entire different race in a source book when IG get one for themselves but maybe the economics works best that way. Who know's maybe later there'll be a Tau source book for Only War eventually.