not all maps would support ships, only maps where ships are wanted enough to warrant the remake would be redone to accommodate ships, and there would be new official maps designed from the ground up for naval combat.
To be perfectly honest, don't wait for naval units. First wait for the OB port, then wait for the "grand empires redesign" release and if you really want you can wait for the aicraft release after that. IF they get that far, i'm guessing the next release would probably further balance airplanes/infantry/vehicle combo and/or be once again a port to the newer engine. IF naval units are still to come, it'll be several years at least before you'll see them. My guess is that before then empires will either move to a completely other engine, or just ceise to exist. People will want better graphics, and empires maps are just too huge to make them good looking in every square meter, at least with the tools provided for the source engine. And i don't think they'll ever turn the source engine in this great outdoor engine with "easy to make" huge, realistic and very detailed environments. By the time naval units can be introduced, people will have gotten used to graphics from crysis 2, fary cry 3, ... etc. Empires maps would still about look the same as they do now.
Yes, like 1% of the people who played it in it's days still plays it now. In the case of empires that would mean one server with 2 people And surely i hope this won't happen, but i'm trying to be realistic, not perse negative. Everything gets old, which is a bigger problem if you have less players "to spare". If 1 out 3 still plays empires in 2 or 3 years from now, that still won't be enough to fill one server, except maybe on a saturday evening. Just try to enjoy what we have at the moment, and give suggestions for the NEXT release or the one after that. Not the one after the one after the one after the one that people thought would've been there a week ago.