I doubt he has started yet. I just heard he is making Warfare 1944, so he probably hasn't started if he is making it.
Yeah I just checked his site and its filled with updates for that game.
Check it out here:
http://www.conartistgames.com/
Anyways yeah he has already made it clear he is going to make The Last Stand 3. In fact here is the direct quote he made concerning it.
Last Stand 3 won’t be like the previous 2, at all. Everything you know and love will carry over, it’ll just be very very different. The whole barricade shooting outward thing is just a bit tired, it’s time to break free.
So yeah thats all I have seen concerning it so far from him. Warfare 1944 is looking good though I have to admit.