Adobe and MS might release UBs for the foreseeable future, but who says the little developers, who really make the Mac experience will? I doubt they will continue to support PPC - they will move to Intel. Everyone trumpeting UB has the be all, end all solution doesn't understand. Why on Earth would people like the WeatherPop people invest in PPC?
Therefore, there's a good chance that software smaller than Office and Adobe's stuff, this time next year, will be Intel based.
The real question is what they will do in the meantime. They have a year in which Mac sales and sales of their software are going to plummit. I'm sure a lot of Mac developers and users are sick of these arbitrary desicions.
I myself won't be buying a new PPC based machine, but if I can find an iBook on the cheap, will buy it and use it til the new Intel based machines come out.