I was planning to, eventually, try to optimize some parts of virtual texturing using OpenCL.
But now it seems someone has done this pioneering work before me!
(using CUDA)
Check out this post from Charles-Fredrik Hollemeersch.
Perhaps some of you may recognize the name as the guy behind Tenebrae.
According to their Poster they seemed to have presented their results at the GPU Technology Conference in San Jose, California.
A chapter about this can be found in the upcoming book
"GPU Pro: Advanced Rendering Techniques"
Awesome.