ARM is scaling up, while x86 is scaling down to get to this future "computing nirvana" where mobile meets desktop. I think x86, through AMD, is going to reach the computer/smartphone conversion line before ARM will. But the problem is the timeframe. Five years for ARM? AMD is at 2.1W for their tablet brazos chip with directX 11 and 64bit today.
Meanwhile, Intel is just pissing around with Atom; their nextgen Cedartrail was thrown together with PowerVR graphics, can't even pass Win7 certification, and can only to 32bit DirectX 9.