Well, I'm actually pretty satisfied with this. A bit lost in some respects, but Urobuchi went the route I hoped and expected he would with Sagara. At this point, him becoming a "villain" or "final boss" would just be tacky. He's clearly not one (like Kyubey isn't one, believe it or not), and I think they went the best route with him. Sagara was going to go to another world no matter what happened, and if these powers granted the ability to be able to "rebel" against him, the past "victors" probably would have done it already anyway. I do have to wonder though - it almost seems like the "worlds" they were talking about this whole time weren't actually alternate universes, but maybe literal alien worlds? I'd assumed he'd jumped from reality to reality, and Helheim just bridged between them, but with how this wrapped up, I have to wonder if, rather than realities it traveled to, it was just traveling to other planets.
Anyway, the three months after bit was pretty well done, and I suppose the last episode will be to either say goodbye to Kouta or to fully welcome him as a true "Kamen Rider" or something.
Then again, once the show ends, I guess that stuff doesn't matter since we have the likes of Blade running around with everyone - on that note, I wouldn't count the Movie Wars out just yet. Megamax hit on a few notes for all three involved shows, remember, including OOO's ending. Core, meanwhile, addresses some loose ends and fleshes some stuff out on the W side, which led up to Accel.