at Build conference, Microsoft didn’t only show Core i5 tablets and the rest of X86 based systems - they had a few machines based on ARM as well.
One of them was based on quad core Kal El Nvidia processor and you can see it live here. It runs quite smooth on this demo
Another thing that Nvidia, a few VPs we talked to recently as well as Microsoft want to point out is that ARM won’t be for tablets only. There will be notebooks with keyboards and processors such as Kal El and they should not cost that much money either. One of them was demonstrated back at Computex 2011 here
So the future of mobile computing are tablets, tablets with keyboards that you can detatch, such as Asus Transformer, or regular notebooks. This is at least a future painted with ARM architecture, and traditionally ARM solutions should end up cheaper than X86.
The real fight starts with the introduction of Window 8 but this will go down in late 2012.