We have nothing to work with at this point. It's virtually impossible to say if the next series will last longer than seven seasons. If the next series is successful, if
, we'll probably get at least 88-100 episodes. With 13-episode cable-style seasons, that gets us seven or eight seasons. I don't know how likely it is but it's not outside the realm of possibility.
No matter how many seasons it runs, I don't think the next series will have as many episodes as TNG, DS9, or VOY.