I am curious about this as well, in light of the fact that I now have the Netgear device, which although not listed as supporting IPv6 on the supported modems list, should support native IPV6.
*edit* and honestly, I'm very unhappy with this speed upgrade thing, too. I know ComcastDJ
were helping drive this, but that was when it appeared to be a modem config issue (which we now know it's not). Don't mean to derail your thread with this, but wanted to point out I am also not very happy with how that has been handled.