Don't hold your breath
From previous experience, Linksys' pace of firmware releases are slower than glacial and are as frequent as hen's teeth. And when they do it'll be for something really important, like a logo change on an admin webpage.. http://cache-www.belkin.com/support/dl/Linksys%20X3500%201.0.01.006%20Release%20Note.txt
Mind you, that seems to be par for the course for most manufacturers of 'leccy-using kit nowadays.