Legendary weapons? Uh... hmm... well... YES.
I'm not sure if Boomeraxe would count as one, since the stats themselves aren't particularly high. The ability makes it nice and handy, though. Quirky and useful could count as legendary, I guess, but that's for PS and SD to decide.
Also, I would have assumed that all weapons retain some level of usefulness at later levels, so useful would probably be less likely to become obsolete than just plain good. Does SAO use a combination of weapon stats and player stats to calculate overall stats for combat? I'd assume that it does, considering that most RPGs do nowadays.
And another thing; I don't know if it's mentioned, but I haven't heard of any weapons having special means of damage. Whether that's elemental with fire, ice, electricity, etc. or using a combination of different physical damage types, like slashing, crushing, piercing, etc. Or whether those different types of damage even exist at all, and if they do, whether they have different effects and effectiveness on different enemies. I guess if it isn't mentioned, there's no harm in making SAO a more expansive game :p
All in all, though, yes. Quest-bound legendary weapons sounds AWESOME.
