ARM (on their website) even discuss larger (up to 2MB caches - which would certainly improve performance). Also ARM may have little choice but to upgrade ARM as other traditionally "desktop" bound RISC processors (such as MIPs and even PPC) move down into the areas ARM "thinks" it "owns".
The five core NEC ARM core (mentioned on Drobe) is another example of lateral thinking on the part of both ARM and NEC. All of this stuff may not be of immediate use - but at the same time I (for one) wouldn't rule anything out). Intel (as this article somewhere mentioned them) have upped ARM performance several times. A low-end version of their IOP331 dissapates 7.5W at 500MHz (at its upper end 800MHz more than that). So to simply have the view that ARM is always going to be relegated to running mobile phones is (IMHO) shortsighted (I don't think you'll find many 7.5W processors targetted at phones will you ?)
As to us "regaining the lead", why is it important to lead ? I'd be happy just seeing a progressive improvement in the performance and capabilities of RISC OS and its native hardware and I think such improvements *are* real possibilities.