Define IMGs.
If you mean by IMGs, traditional IMGs who went to a school in Europe or India, are foreign nationals, and require a J-1 or H-1b visa, then I'd say that the situation has always been tough. And, yes, it's going to get tougher.
If you mean IMGs as in U.S. citizens who got their education abroad (either Caribbean or elsewhere), I think that is a slightly different story. There are going to be far more schools open in the U.S., as Chris Griffen alludes to, which means that there will be far more spots available for those "near misses" who didn't quite get into medical school in the U.S. These are usually the students who do quite well at Caribbean programs and "make the grade" (so to speak) and get into U.S. residency afterwards without a problem. There has been a concentration of states where this has occurred in the past, and these matriculants will have more opportunity to get into a U.S. program.
What will be left-over will be the students who, even now, struggle at Caribbean schools. Yes, programs will still exist for that cohort. And, yes, I think that these students will likely continue to not do as well as their otherwise "near miss" counterparts.
This is bad for those students, and it is bad for Caribbean schools in general. Overall, more U.S. spots is a good thing for people who would otherwise have had their education in the U.S. but were forced, through an artificial cartel imposed by the AAMC and COGME for decades that has now come back to bite the U.S. in the behind (you can never argue with demographics, as my dad is fond of saying), to go Caribbean because they had no other options. Now they will have more options.
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