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.