Look at Ric's first post here. 'Camelot, the makers of GS for AGB'. Why don't they tell they also made Mario Tennis and Golf for the N64??
And Mario Tennis was almost perfect, how could they improve it???
But yes, a new sports game would be nice.
But a sequel is always easier than a totally new game.
My guess is they're already working on a new original Mario Sports game. Baseball or something...
Edit: Hey, that was a thoughtfull post!!
(hint hint)