Those suits are sort of iconic for Super Mario Bros. 3, they're exactly what you think of when you think of it, and with good reason; they were freaking cool. That said, I really don't see them coming back in Super Mario Galaxy 2. Maybe NSMBWii(although it's got it's own range of powerups so far), but just not SMG2. Most of the SMB3 power ups have equivalents in Galaxy already:
The shell helps you swim like the frog suit.
The spring helps you jump like the frog suit.
The star spin is like the racoon spinny attacky thing