Should you drink Draino?
Seriously though, most X1 exclusives go to PC now, so for you I don't see much of a point. If you want to play the ones that are left, like Sunset Overdrive for example, you need to evaluate what it is worth to you. If it is worth 300 dollars, then sure. This is something only you can answer.
However if you have a PC, PS4, and WiiU I would say your gaming needs have been met. Thats just my 2 cents based on your situation.