I don't think titles no longer being exclusive to consoles is going to hurt the games, or the consoles. PC and console don't really compete, at least not as much as the PC Master Race (ugh) guys would like to think. They're at home in different play environments and people are going to choose based on which environment suits them, not the exclusives. Exclusives might decide if someone is torn between a PS4 and an Xbox, but in most cases they're probably not going to be the key deciding factor that turns someone from a PC gamer into a console gamer. It's going to be based on their preferred input methods, whether they like to play on the sofa or at a desk, what they can afford, and so on.

So PC sales aren't missed console sales - they're new sales that probably wouldn't have happened at all if the option hadn't been available.

On the technical side, console and PC hardware and software (particularly in the case of Xbox) are very similar these days, and with the addition of things like UWP it's even easier to make things work on both platforms. Plus, typically it's PC ports that get the short end of the stick when things are ported, so I wouldn't really worry about the Xbox editions losing quality because of it.