It's hard to say if Samsung will return to the S5/Note 4 design form as the current design language on the S7 and S7 edge has been pretty popular, especially the latter. Given that a lot of their phones have a similar design language, and how well the S7 is selling, it's unlikely at this point that they'll do another overhaul of their design. Maybe a few more improvements here and there.
Another thing is that if one truly wants to bring the Note back to its "glory days" of having a removable battery and back cover, the S-line device has to have those first, as the Note (aside from the tablets) is usually based on the S-line device of the same year. Whatever the S-line device gets, it's likely that the Note will pick those up as well, along with its own stuff, since both are part of Samsung's flagship line. Or make the Note drastically different from the S-line, though that does bring in its own set of challenges.
We'll see next year. Maybe there's a surprise hidden in store?