That's just wrong. IPv6 doesn't need any other hardware capabilities than IPv4. There is absolutely no technical reason why it should not be possible to give the router IPv6 capabilities, as this is done in software entirely.
Many other router manufactures do so, e.g. AVM has already released IPv6 firmwares for older router models in 2009!
The only reason is, they want us to pay again for a new router to get IPv6 support. I bought my DIR-655 november 2010, I won't buy another DLINK router the next 3-5 years for sure. If the internet is completely switched to IPv6 in the next few years, and a big company like DLINK will let me alone without support, with no access to the internet with a router from 11/2010, then DLINK is just a poor company with no products worth to pay for.