Since Bethesda decided to dedicate each game to each province of Tamriel,I believe there will be at least 9 elder scrolls games,counting from Morrowind on.
I don't think they have decided to dedicate each game to each province. Skyrim is taking place in all of Skyrim (see the GI tour of their offices and you can see the map they're working with - it covers the entire province) and Oblivion covered all of Cyrodiil, but Morrowind only covered a relatively small portion of the province it was named for. Even Oblivion wasn't really dedicated to Cyrodiil, it just seems to have taken place there because... well, the plot was dealing with major world-changing events that couldn't have really taken place anywhere else. And that's to say nothing of Daggerfall (which blends regions of High Rock and Hammerfell), Arena (which covers the entire empire), or any of the spin-off games (which mostly take place either in a single dungeon or in a smaller region within one of the provinces).
Given how they handle the series, with pretty significant changes in their approach and in what they try to "innovate" with every title, I really wouldn't expect them to labor through each province one by one. I'd actually be surprised if we go a full six titles after Skyrim without getting another that tries to cover all the provinces again (or that's released as a sort of platform and includes one region, with DLC or expansions developed to add more regions to it in the same way that GTA4 has DLC "sequels" of sorts).
Either way, the Elder Scrolls (as in, the actual scrolls within the universe that the series takes place in) don't contain just five prophecies like the first poster said so it's sort of a moot point. They contain the entire history of Tamriel, including events that haven't happened yet. Even with that aside, Bethesda wouldn't kill a cash cow for the sake of preserving canon.