Why? A software solution for virtual texturing is already working on non-hUMA hardwares. Rage for example.
The tiled resources function in DirectX is also works with any hardware. There are three tier for it. One software and two hardware solutions (a limited tier1 option for Kepler, and a full feature set tier2 option for GCN, and also for the consoles). If you use a Granite middleware for it, than the compatibility won't be a problem.
hmm could be like this:
other GPU --> software solution
Kepler --> limited tier 1
GCN 1.1 ---> tier 1
GCN 2.0 --> tier 2
even DX 11.2 will exposed some of GCN 2.0 features,
the upcoming DX will exposed more and more GCN 2.0 features
no wonder some forum said that they are testing DX 11.5 or DX 12 alpha
(some russian forum)
also it is strangely Hawaii Lauch date is same month as Windows 8.1
Hmm if tier 2 relate so much to GCN 2.0
then X1 is must be a very custom build of GCN 2.0 as a base