Given the pace at which Qualcomm chips are getting faster (much higher than for Intel ultrabooks), there is no doubt that ARM will soon outperform Intel at equal and even lower TDP. So in 2-3 years we'll have chips that are natevely faster than Intel quad core U chips (general windows use, Edge based on chromium, office etc.), that is to say a speed like what the ARM chip in the ipad pro already has, around 18000 in multi-core Geekbench, while showing maybe dual core like performance in Emulation (that is around 8000-9000 with the same benchmark). This could be a big hit in the market if priced reasonably, contrary to what OEMs have done so far (selling at extremely high margins).
We probably need these chips to fall in the hands of Chinese OEMs to get prices down...
One way or another WOA is likely to be a big part of the ultrabook future in a 5 year horizon.