Doesn't make much sense to me from a marketing standpoint. It's almost as bad as "Wii U." I think 720 would've been better since it's 360 times 2. When I hear "Xbox One," I think the original Xbox, like people say Sonic 1 when referring to the original Sonic game even though it wasn't actually called "Sonic 1."
They didn't call it Xbox 360 just for the hell of it. It was something about a 360 degrees experience or something. No point in calling the next one 720, since that'd just be another 360. Still, I see your point in how ignorant consumers might get confused by naming it "Xbox One."