Well, the way I see it - Chewbacca is already established as a 200-year-old character in the OT.
Obviously, the events of the PT had dire consequeces for the whole galaxy.
Chewie was alive to remember the Clone Wars.
Even before the PT was written, Chewie's established age made this a fact.
IMO, it is better that Chewie be shown in this context in ROTS - better him than Han, Lando etc etc.
It makes sense to see the Clone Wars and the formation of the Empire influencing a species we know from the OT.
It gives us an anchor.
Otherwise we just get to see battles on Saleucami, Mygeeto, Felucia and Cato Neimoidia.
Where?
Exactly.
Personally, I don't really see the problem...
Besides - the struggle between the primitive Wookiees and the technological Empire was the battle Lucas had always wanted to bring to the screen, from way back when SW as we know it was still a twinkle in the flannel one's eyes.
Okay, so that battle is not quite what we are getting, but I'm sure it will be fantastic - it is a real labour of love.
part of me likes to see ot characters in the pt.....part of me worries that it's forced and tacky (anakin building 3p0, greedo, jabba etc.).....in cas4 anyone wasn't aware, there's a recent rumour saying they attempted to put han in ep3 but couldn't pull it off and cut it.....kinda glad they did....i was worried about chewie in this film to start with, but i'm relieved to say it seems to make sense to me, and doesn't feel jarring at all really.....why wouldn't yoda be fighting on kashyyyk?.....very relieved....
I never really thought about it but PVS is exactly right about the Obi trusting chewie thing, Lucas did say that there are alot of things that we may not have noticed in the OT that we will look at diff. after ep.3, this could easiily be one of those things, and although obi and chewie never came in contact if chewie helps to save yoda im sure yoda told obi off screen