I'm extremely looking forward to Inception. In my opinion Chris Nolan hasn't made a bad movie yet, and furthermore -- and this is what's really exciting -- is that he keeps on getting better and better.
I'm not that worried about the box office of Inception, not that is really matters anyway. Even if this movie bombs -- which I highly doubt it will -- Nolan is still pretty much locked as director for Batman 3 given the monumental success of The Dark Knight. The only thing that will be detrimental is to WB, obviously, who invested in the film, and Nolan, who might have to make smaller movies if Inception doesn't do well, but hell, I don't think that would be much of a problem either, as Nolan's smaller movies are usually his most interesting.
Inception looks like it might be the ultimate Chris Nolan movie -- packing the intelligence and plot experimentation/sophistication of his earlier movies like Memento and The Prestige with the big-budget awesomeness of the Batman movies. My hope is that if Inception does well, Nolan will truly be given cart blanche and we'll start seeing even more intellectual blockbusters. After an abysmal summer, we definitely need them.
I don't see Toy Story 3, The Last Airbender or Twilight as threats. Toy Story 3 has been out for a while and while it'll still do progressively big business, the "awe" factor has been diminished since it's been out for a while. The Last Airbender received some truly horrendous reviews, and even worse -- a fan backlash -- so I think it'll dip poorly next weekend. Twilight is also showing signs of weakening as a franchise since it didn't open to expectations, and I see that movie fading relatively quickly to make way for new blockbusters, like Inception.
It'll be tough to see whether or not Inception will be a true box office smash, but with these immeasurably incredible reviews mounting up, and the fact that this is the director of the third highest grossing film of all time, I don't think we have to worry about the prospects of Inception. At all.