Last COD game? no way.
Call of Duty has become the mother of all milking cows.
They will more likely release a COD game every year. No way this will be the last, there's too much money to be won.
Last game on PC?
I doubt it, altho the main focus of the developers is clearly the console market, and despite the piracy on PC, there is still too much money coming in from the PC gaming community to stop supporting it.
What will happen more and more tho, as is already going on right now, is that the games will be developped for consoles, and the PC versions will be direct ports.
PC specific features, like dedicated servers, mod support etc, will likely, and sadly disappear.