I don't understand why people who have recently bought a Mac should be upset!
All major applications will be compiled for both PPC and X86 for at least the next four or five years, if not longer, considering that Apple intents to keep shipping PPC Macs until 2007. Even brand new applications developed with Xcode will support the PPC, as in 95% of cases it won't be any extra work at all to compile for both.
The only effect will be that developers will stop optimising code specifically for the PPC, and if certain API features eventually become X86 only, developers will start to drop support for the PPC, as happened in the 68k to PPC transition.
But this won't happen for years. I expect that a PPC Mac will be able to run almost every single application released within the next four to five years, and most applications even after that.
Having said all that, convincing potential customers that this is the case over the next two years is going to be difficult for Apple.