I agree that something like the Pennsylvania plan to throw electoral college seats to Republicans will happen at some point, probably in the near future. The presidential election system was a horrible botch from A to Z, based on several assumptions (most notably an opposition to parties and a fear of popular control) shared by a party that virtually died after 1800 and that were anachronistic almost as soon as the ink dried on the Constitution. And so it stopped working virtually from the beginning. A serious of norms has emerged that has allowed the electoral college to, with notably rare exceptions, produce results that approximate ones that a well-designed, democratic system would produce. But the horrible design is still in place with plenty of potential for mischief, and eventually someone will find the prospect of temporary advantage irresistible.
…to be clear, the problem with the Pennsylvania plan isn’t that apportioning electoral votes by district rather than winner-take-all is inherently bad; indeed, it’s arguably better in itself. The problem is when it’s done selectively by a major state rather than uniformly, which could lead to a huge loser in the popular vote winning the election. And, yes, it would be just as problematic if a Democratic-controlled Texas had done it.