There are a lot of signs that Google wants in on this mobile advertising game. I think they realize that's where their future bread and butter is. But I want them to start promoting their .mobi!! I think they will, in time.
Agree ... if they weren't a "backer" of mTLD, then I don't think it would be such a big deal that they aren't actively developing -and- promoting their own .MOBI, IMHO.
However, since they are a "backer" ...
Google is so powerful that if they were to start using their .mobi and promoting it then everyone else will most likely follow. I am sure they will always use their .mobi since it costs them pennies to make and maintain but the key is if they advertise and promote it in the future.