In that regard, the excellent Paul Thurrott (who I've linked to occasionally) has a very interesting discussion on these Bay Trail tablets -- that merge both versions of Windows -- compared to what the Surface 2 tablet uses, which is not only that app version of Windows only (known as Windows RT), but also an ARM processor, rather the more standards Intel. In a very clear, user-friendly way, he explains the differences and why he sees the advantages of Microsoft slowly positioning Windows to this ARM and Windows RT technology over time.
None of this is imminent, so don't worry. The legacy Windows desktop on Intel is here for a long-enough while. But Thurrott explains how ARM technology is faster and cleaner and more stable, without the threat of viruses, and that eventually desktop programs will be available for it.
It's quite interesting and well-done. You can read the whole thing here.