To be fair, the new client isn't being made only to allow for 60 fps like some of you are making it out to be.
From my conversations with higher ups it's primarily being made because working with Stefans 15 years of patched code client was proving too much of a hassle for anyone not being Stefan himself. Yes, 60 fps is nice, but having an engine which code you can work with for future updates is so much more valuable. Who knows, since it's Unity based we might even see the rebirth of a Linux & Mac client!