"Just shift back" is really underestimating how much effort it takes to port a design to a different foundry. Sure, you can target a new stdcell library and recompile your RTL (and re-floorplan, and re-do a bunch of other stuff) but you also have to swap out all your memories and interfaces, not all of which may have exact equivalents... it can easily take 1+ years of work for a competent team, and if you have to shift back all that time and effort was wasted.

And just hope they have any capacity to deliver? That's what I'd worry about, especially right now.