Nathan Brookwood analyst from Insight 64 asked Intel about the lack of 64-bit support at launch, and it turns out that Intel doesn’t have it, at least not in the first batch of Bay Trail parts.
Intel plans to support Windows 8.1 32bit version for the rest of the year and it said that support for the 64-bit version comes in the first half of 2014. Since apple A7 is a 64-bit processor it turns out that Apple is a step ahead and so is ARM.
Intel will certainly catch up, but it turns out that people really care about this. Avaton, a server version of the chip supports 64-bit operating systems as these are the ones that need more memory, but eventually this will also extend to tablets and other devices based on Bay Trail-based Atom, Celeron and Pentiums parts.