I just got my PHB3, and there doesn't seem to be any language that specifically addresses this. My guess is that it's possible, but I'm wondering if there are any rules that cover this directly.
A wizard buys a mindwarp staff (superior implement) and then adds a weapon enchantment (e.g. Vicious Weapon) to it via either Enchant Magic Item or Transfer Enchantment.
As far as I can tell, a superior-implement staff is still a quarterstaff and thus eligible for the enchant, and adding a weapon enchantment to a superior staff wouldn't turn it back into a regular staff.
A wizard buys a mindwarp staff (superior implement) and then adds a weapon enchantment (e.g. Vicious Weapon) to it via either Enchant Magic Item or Transfer Enchantment.
As far as I can tell, a superior-implement staff is still a quarterstaff and thus eligible for the enchant, and adding a weapon enchantment to a superior staff wouldn't turn it back into a regular staff.