I don't think I've seen or heard them mentioned in a good twenty years
Har
Completely serious
They were brought back in NSMBW after much fan demand. Then they were subsequently put in NSMB2 and NSMBU in the same capacity with extremely similar battles, and people got weary of them. Then they were put into Mario Kart, taking up a lot of the newcomer space in that game which pissed some people off and they wound up getting in Smash as well. At this point the general consensus is too much Koopalings.
Personally I want to see them get a 3D outing.
Their first comeback was in Mario & Luigi: Superstar Saga. ---