It depends when they exit the competition. Get to the final and it's touch and go if they will be available for the start of the season proper never mind China. There is far too much football these days in terms of player burnout at least. Moving forward you will probably see larger squads and player interchange in matches. The purists won't like it but with the current pace of the game it seems inevitable. Also you may see a move towards a six year cycle. That will mean WC/Euros every six years rather than 4. But we will see.
That would be a huge loss of revenue for uefa and fifa. I just can't see that happening. You could argue that club football might force the change on those two but honestly if you're willing to go that far then TBH it's far more likely that they would call for the scrapping of the tournaments altogether - but I don't see that happening.