That'd technically be a two-cour "season" stretching the length of two typical seasons, and considering how mediocre Maidragon BD sales were (not necessarily bad considering the relatively cost-effective way in which Kyoani produces anime but still not really "good" per se) combined with the relative lack of official merch, I think that the absolute most anyone could reasonably hope for would just be another standard, one-cour season. I don't see any reason why Kyoani would decide to upgrade an S2 to two-cour status. It just doesn't seem like they'd make any real return on such an effort especially when they could probably just make more Free! or even VEG (the latter not really being THAT huge, but it's at least still relatively fresh in people's minds) if they wanted to cash in on something.
All that said, yes, a 24-25 episode S2 would most likely be enough space in which to fit everything up to the resolution of the current manga arc with maybe even some leftover space for spin-off material.