There is a lot of new hardware out there. Most manufacturers don't even do real updates for their own phones; I can't imagine what it would take to get WebOS running on the variety of hardware in circulation today.
And in this case, having a 2009 v 1.0 phone OS running on new hardware surely isn't sufficient. Our ideas of what a phone should do have expanded significantly. So we're really talking a large development effort. One estimate I see says Apple has 1000-2000 people working on iOS. Given Android's much larger hardware ecosystem, I'd bet the number of people working on Android one way or another is larger.
Matching that with an open source effort seems implausible to me.