The first thing problem would be the brand-ownership/distribution issues. Altadias owns lots of the brands, but not all...General holds several, including most of the bigger names, and of course MATASA holds one as well (Fonseca). It may take YEARS to sort out those very complex issues.
After that, then you've got the potential quality drop off, which while not certain, COULD happen if Habanos SA decideds to radically increase production to meet the increased demand. Sure, lotsa CCs already end up here in the US, but if the embargo is lifted, every Tom, Dick, Harry, and Jane will want to buy Cubans. We could experience the same kind of supply/demand problem that happened during the boom--not that I was around then, but I've heard plenty of stories about those years.
Last but not least, there could be a substantial price hike; I'd bet that Habanos SA could put whatever price they wanted to on Cuban cigars and they'd sell like hotcakes regardess. At least, they could for a few years till the excitement wore off.
But of course, all that is conjecture. :yes: