1) Yes, there was a lot of Oscar buzz for RENT and it all didn't just come from BroadwayWorld.com. Lots of Hollywood pundits were expecting Adapted Screenplay, Sound, and possibly acting nods.....VERY early on. As the film came closer to release, that all went away.
2) It's never too early to say "this person has a shot at a nomination" but to already narrow the list down to five is idiotic. LITTLE MISS SUNSHINE was an expected surprise this year that ended up becoming an Oscar-winning film. We never know. Over a year ago everyone said "Bill Condon + Dreamgirls (+Foxx and Murphy) = Oscar" and look how that turned out. Right now, we can say "Tim Burton + Johnny Depp + Sondheim musical = Oscar" and we won't know until the nominations are announced.
It all depends upon the stars aligning. As I said earlier, it doesn't matter if Depp is brilliant. It matters how the film is received and what competition there is this year.
3) Plum, must he be baritone? Perhaps Sondheim has rewritten it to fit his voice?
4) Brody - both RENT and PRODUCERS were expected to earn Oscar nods early on. I already mentioned RENT, but PRODUCERS was expected to possibly nab Best Picture, Adapted Screenplay, acting (especially Kidman for Supporting, which turned into Thurman), Best Song, Best Costumes, Best Sound, etc. As I said, as the year progressed, it all dwindled away as people saw what those films really were.
"The Spectacle has, indeed, an emotional attraction of its own, but, of all the parts, it is the least artistic, and connected least with the art of poetry. For the power of Tragedy, we may be sure, is felt even apart from representation and actors. Besides, the production of spectacular effects depends more on the art of the stage machinist than on that of the poet."
--Aristotle