^1+
This has been discussed many times over the last several years, and yes, the general consensus is that quality would degrade considerably.
The Cuban economy has disintegrated. Corruption is widespread. The state-run agriculture sector is starved for investment.
Create additional demand on that of even 50% and what do you think will happen? Opening the US market to Cuban cigars will create such a demand that they will be sold out quicker than Stonehaven, and the quality will be of a gas station Swisher. Remember the fable about the Goose that laid the golden egg?
It's a similar story to what I read about Samuel Gawith and Esoterica: a good product that was once regularly available, became much less so, and now generates a piranha-like chaos whenever they are released to the market. Unlike SG and Esoterica, I was able to stack boxes of some favorites, so if the embargo ends, it's no concern of mine as I can weather several years of poor availability and speculative pricing.