Depends what they mean by "maintenance". I suspect they don't mean the maintenance of the Magic Bands themselves or the readers that use them) themselves. I think they mean the maintenance of the "reservation" system and all the IT work behind the scenes for it. So I think the maintenance comment doesn't meant the Magic Bands .. it means the FP+ system itself.
I could see WDW switching to MaxPass (but keeping the Magic Bands themselves for a few reasons).
1) No "maintenance" of trying to keep track of every guests Fast passes for 60 days.
2) Making things more "equitable" for all by letting every guest only be able to make Fast Passes the day of.
3) Ability for Disney to be flexible in changing schedules and such up to the day of without having to worry about cancelling people's fast passes.
4) Less guess complaints when book a resort stay, log in at the zero hour on Day 60 and still can't get the Fast Passes you want.
5) Able to charge for Fast Passes like they do at DL.
Personally, I think a lot of us would prefer a MaxPass type of style. A lot of people don't like having to plan everything 60 days in advance. Less flexibility in a touring plan.
Though .. I think there are also a lot of guests as well that like the ability to lock in three "skipped" rides and just forgot about it rather than being glued to their phones during the park day.
For a first time goer, FP+ is awesome, for a veteran or annual Pass Holder, something like MaxPass (or the old paper system) is probably better.
I don't see them abandoning FP+ though . .it is a huge part of their marketing and they have shifted the guests to know and expect it. To ditch it for a "day of" type of system (and/or start charging for it) . .that would be a huge backlash.