I wouldn't say "enough," because there has only been 3 Paper Marios and 2 Mario and Luigis.
And soooo....3 Paper Marios+2 Mario & Luigis = also 2 Super Mario RPG!!
Then there isn't 2 without 3! So There will be another Mario & Luigi + other 2 Super Mario RPGs!! X3
I'm sure they will do a sequel of Super Mario RPG, because it is one of the greatest games of Mario of ever! This is sure!
..But I don't know when, how, who, which one...what?@_@
Nintendo also takes cares of Mario RPG characters, especially for Geno! Who can forget the Geno cameo in Mario & Luigi Superstar Saga?
Finally I think they are thinking of making somehing with a new Mario Rpg...maybe...
Now God knows, not the fans! XD