I have wondered about this myself and think there are a few things to consider:
1. A lot of Americans are already getting cubans from online stores (eg variouis swiss vendors) sending them in without bands etc
2. Americans don't like paying much for their cigars. I'm writing from Australia, where we pay a fortune, but time and time again see Americans online complaining about much cheaper prices being too much
3. I'm not sure that all Americans will prefer Cubans. I have smoked my way through most of last year's CA top 25 (only three cubans on the list), and didn't get over excited, which could be because I've grown up with Cubans, which have a very different flavour profile. I wonder if the American smokers who have grown up on the non-cubans will be the same with Cubans?
3. The Chinese - has the cigar market there taken off as much as the premium wine market has? I would imagine that it has to some degree and we haven't seen a huge price rise as a result.
I guess these are all arguments against a huge increase in demand, at least after the inital novelty phase. Having said that, I would be putting my money on some permanent increase in price