Intel fabs aren't going to be simply abandoned. In the absolute worst case, they'll be spun off like AMD did with GlobalFoundries back in 2008. And GlobalFoundries remains a major player in semiconductors even today. It just doesn't chase the highest-end nodes.
EDIT: I should also add that spinning off the fabs, while bad for Intel as a whole, would probably be a net gain for the rest of the industry. A major sticking point right now is that third-parties don't want to fab with Intel because they're afraid of IP leaking into Intel designs. If Intel's fab business was completely divorced from Intel itself, it'd get a ton of extra business. Nvidia and AMD would love nothing more than to have a second-source for their stuff that isn't TSMC.