This year, Intel will launch its Haswell chips. One of the most important performance improvements of Haswell will be power efficiency and battery life. Meanwhile, Microsoft created Windows RT to run on ARM-based chips for better battery life. Microsoft's Surface RT runs an NVIDIA Tegra processor, and has better battery life than the Surface Pro, which sports an Intel chip.
If Haswell can live up to Intel's claims about the battery life improvements, there simply won't be a reason to have Windows RT around any more. Unifying around Windows 8 would benefit both Microsoft and Intel, while removing consumer confusion.