This just seems odd to me. I know it’s a competitive game, and most folks will be playing with a mouse and keyboard, but it feels weird for Valve to put out a brand new game (built from scratch, at that) and not plan for this.
Preface: I am no game developer, but I am a software developer
This comment does not make sense to me. There is no "simply" bringing any game to any other engine. Doing this is a huge undertaking and I can't imagine not basically starting from scratch, saving the art assets and bits of pieces of the code (given it's written in the same language).