Whatever you decide please don't give Microsoft money for a windows licence if you can avoid it! As was mentioned do they really care what you run as long as they get their money. So although I originally questioned the need to run Riscos under Wine under Linux since you might as well be Linux native for all you THINK you gain, if you really must run RiscOS under emulation then do indeed choose Linux+Wine.
The x86 CPU is not the only one that can satisfy higher demands. It just happens to be the one with the most investment (due to volume) and thus is proceeding apace. The ARM CPU on the other hand only has to satisfy the demands of the mobile market and thus the demands for power there are much lower. However, the mobile and low energy demands are changing and you should expect to see a change there.
Linux is playing catch-up? It sure is but it is succeeding whereas RiscOS failed. Mac was also playing catch-up and has already succeeded. The latest evidence from sales is that Mac's are increasingly the machine of choice at the expensive end of the PC market. Linux is at the cheap end but going upwards. In the middle you have Microsoft who are losing market share quite quickly. Hardware manufacturers can see this and are now providing drivers for all three platforms.
Microsoft DEFINITELY IS losing at long last and you will see Apple and Linux side by side in PCWorld any day now. Ubuntu Linux that is.....but hey that's another story.
Should Wine improve to the point where the vast majority of PC games run (very roughly 50% at present) then you will see more pure Linux take-up. Wine also runs on Macs. Microsoft is petrified look at its behaviour!
Please note folks, take some time to trawl the Mac+Linux forums and get a feel for what is happening. AMS opinion is a little outdated.