i don't think the team is built around hiruma, most of the guys came to the club because of sena. (And it was Kurita who wanted to start a club, remember?) I think making a devilbats without the third years would be like killing of a main character in a shonen series. It would be hard to continue, but if you are good enough you can pull it off, and i think the writer is good enough.
Not to mention that hiruma and co are not gone forever, they just can't play anymore, so we get room for other interresting players.