It's alright saying you'll invest more (we've heard that before) but what happens if those games fail? They'll just go back to Halo/Forza/Gears on repeat (again, seen it all before). They have to be serious and really build first party studios that can put out variety and stick with it even if they don't sell Halo numbers. It's going to take a good generation to build these up and TBH it all seems too little, too late. So far, going into the next generation, MS have no new worthwhile IPs to expand the userbase beyond what it has now. While Sony are building up new and exciting IPs, some of which are very big games turning into blockbuster franchises, that lots gamers are excited to play the next in the series.
MS should have started investing at the end of last gen, and building upon them this gen. But we are most of the way through this gen, certainly by the time any potential new IP can be launched, with so far just talk and no action. All eyes are on E3 for them to pull something interesting out of the bag. I'm not holding my breath though.