By your logic then the 6.5-06 makes the 6.5 cm obsolete. - dan
It would be a great competitor if it was commercially available, hell I'd buy one in a heartbeat, easily formed from common brass, good jump in ballistics over the 6.5x55, but unfortunately very few makers put guns out in that chambering. Now if Hornady shortened the 6.5x63 to 6.5x55, blew it out to straight wall with minimal taper, and put a 30 degree shoulder on it, and called it something else, the unwashed masses would be all over it as the latest and greatest lol.
Same goes for the 6.5-284, that's probably easier to find, but still a better cartridge in long action vs stuffed into a short action.
The 264 Win should have been the 6.5x55 dethoner in North America, but I guess the 6.5x55 mild recoil, accuracy, brass and barrel life was more appealing to folks. It seems to work fine as is for 120+ years, hard to make something better with that kind of track record.
There will never be another cartridge with the history, popularity, and loyal following in 6.5 as the 6.5x55 has...ever.