"It is certainly a more expensive task developing 32bit updates than many people think. I estimate a high four, or low five figure sum."
This radically depends on the size of the product itself, of course. I'd estimate that it'd take nomore than a day to fix all the bits of assembler in Slayer, for example. (Fortunately, it's mostly BBC Basic, like the other two major RISC OS AVs)
One of the other advantages of moving to 32 bit RISC OS is there are many less viruses that will actually work on it. Still, if people want a 32bit Slayer, I'll look into it, but it'd likely need rewriting from scratch (and it'd be much simplier because of it.)