I agree it probably could go above 100 dollars but I don't think people will be able to comprehend the cost of items being sold at .001 bit coins or .0001 which will hinder its ability to go higher.
You must be a bit newer here. The fractional thing isn't an issue, there are people already working on sub-units. The bitcoin itself was designed with deflation as a possibility.. so in the future we may be doing 1 millicoin = 0.001 BTC or something.. the bitcoin software will just get updated for that, if the requirement should arise in the future... so it's a non-issue.
I can tell you just by looking at the trading ladders that one big player could push the price of bitcoin to $50 easily... if someone wants to do that. By big I mean someone with a million, who feels like taking a big speculative position. The bitcoin market is really in its absolute infancy, when you look at the bigger picture.