I think the next Smackdown game will be called Smackdown vs RAW Pain is Glory but I'm not sure.
No legends can't be used in season mode.
I don't know why there isn't tag titles or hardcore belt in the game but there might be tag titles in the next Smackdown game but no hardcore champion.
Titles suppsed to be in the next Samckdown vs RAW are as follows.
WWE Champion
World Heavyweight Champion
Intercontinental Champion
U.S. Chapion
WWE Tag Team Champions
World Tag Team Champions
Cruiserweight Champion
Womens Champion
Teddy Long might be the GM in the next Smackdown vs RAW game.
Hope I helped.