My previous reply was aimed at kybernetikos and Stoppers.
@AMS: There are many reasons to go for a hardware-independant version of RISC OS, not just the performance of ARM CPUs. Even if high-performance ARM CPUs suitable for desktop machines were available, we probably would not get a RISC OS machine with such a CPU, because the RISC OS market is too small now. And someone did produce such a machine, it would be way too expensive.
Yes, ARM has been trying to get higher-performance chips out for years, ever since the ARM1020E (ca. 1999?), actually. But nobody wants to produce them. When chips with the newer ARM architectures are released, they have usually been highly customised for some embedded purpose and are not very well suited for desktop use.
To grow the RISC OS market again, anyone would have to be able to run RISC OS on their existing machines. This are usually PowerPC or x86/x64 computers. If we could grow the RISC OS market again, we might even end up with new ARM desktop machines, for peaople who like low-power-consumption, quiet computers.
I find the possibility, to turn any hardware that can run a Linux kernel into a RISC OS machine, quite attractive.