This seems like it's a much bigger bombshell than Kotaku is treating it.
If Yu has really taken Gearbox over and set it up as the heir apparent to the Halo franchise, that's monster news!
"I was offered and recruited to the position of Principle (Lead) Engine Architect of Halo Franchise Team at Microsoft. I accepted the offer to lead the team to build the engines and games for future Halo's on Xbox'es and PC's at Microsoft." -Corrinne Yu
I think that pretty much says it all right there. And personally, I think Gearbox is a pretty good choice if MS feels that Bungie can't (or doesn't want to) handle their flagship anymore.