Thats exactly what people will do.
But, I assume, since the current quixel library is free for all engines, that it will become the “free content” in the future that is mentioned in the announcement.
Any additional (new) content will probably be paid only.
That said, these are only my thoughts, nothing official. (but it would make sense, given that everyone who wants it will have the current stuff “soon”.)
If I am right with my assumption, that would be a very fair (generous) way to transition, I think.
Maybe we can also get some insight on this?