They said the same with the Intel transition, and also projected a two year timeline. The transition was over much sooner than that and there weren't any new PPC products to speak of, as far as I remember. And of course, PPC Macs only got one more version of OS X before support for them was dropped.
They're just trying not to Osbourne themselves too badly. They want you to keep buying Intel Macs, but who's to say how long they'll keep support.
PPC was complicated by coming after years of failing to have decent chips actually ship. In this case, Intel and AMD are both still heavily invested in pushing x86 forward and Apple doesn’t have to do all of the work maintaining things like compilers or the JVM so it’d be a lot easier to keep that option alive if there was a good enough reason.
They're just trying not to Osbourne themselves too badly. They want you to keep buying Intel Macs, but who's to say how long they'll keep support.