A few words of clarification: First off, while I was peripherally involved with the initial migration of all powerpc support to use a device tree, the credit for most of the heavy lifting goes to others like Paul Mackerras, Ben Herrenschmidt, Becky Bruce, David Gibson and others. I'm building on their work, and many thanks go to tbem.
Second, while I know that Canonical and Linaro are both committed to device tree support, I cannot comment on Google's plans. As it stands, Brian Swetland from Android has eloquently expressed his skepticism about the device tree approach and has no intention of using it (which is fine; the current code allows dt and non-dt platforms to coexist. Board ports are not forced to use a dt).