This is good news. As Canonical is now the primary vendor pushing AppArmor as a security solution, its vital that they take responsibility for it. And they clearly have been doing that. I look forward to seeing the inclusion of this raise their profile in next years kernel developer statistics report.
Regardless of any arguments for or against multiple security models, if its going to exist..having it in the mainline kernel is the right way for it to exist as a maintainable solution.