I first thought - well, they use the AMCC 460 in their current products.
So is there an AMCC 500 series chip? Turns out that currently there isn't.
Anyway, the AMCC 460ex actually uses a PowerPC 440 core. There is a PowerPC 460 core as well - the AMCC APM86190 uses two PowerPC 465 cores at up to 1.5GHz.
There is also a PowerPC 470 core, but it doesn't appear to be used in much. You can get quad-core at up to 2GHz or so on a 45nm process apparently.
It's only a couple of weeks away, probably best to wait to see what they're up to.