Which will be interesting because if we consider how fast the 99 days are passing, he might be revived mid-season. Which could make a pretty interesting plot, the main rider suddenly losing his power...?

I know W left it to where they can still use their powers. I haven't seen any of the OOO movies, but doesn't he gain his powers back after the last episode?

He regained his power in Movie Taisen Mega Max, where Ankh and the medals reappeared from the future. As it was never specified when exactly he and the medals will return, Eiji technically has a chance to have had them back for all his appearences afterwards- though Ultimatum suggests that he didn't have them back yet because he didn't transform in that one (and the OOO that appeared was created by the Wizard rings).

Fourze and Wizard kept their powers, but Ultimatum suggested that Gentarou might give them up in the future. Gaim also still has his. Drive lost his powers, though Belt did say he would return when needed, which happened in the Final Stage, for example.

As for the Pre-Decade Riders... I think the only ones who explicitly lost their powers at the end of the show were Ryuki and Faiz, the latter actually died, according to the Yongou special, but the Faiz Belt can still be used by any Orphenoch, so the Rider can still appear- it just isn't Takumi anymore.

No idea. I'm mostly basing my assumption that they all get to keep their powers on the fact that they all have a Movie War after the series, and a whole crossover movie in which the old Rider can't transform would be kind of boring. I suppose they could always make it so that they do get their powers during those crossovers though, yeah...like Takatora, I guess. So I guess Takeru could easily lose his powers at the end as long as he gets them back by December...

But the movie war doesn't bring their powers back permanently, as happened with OOO in Megamax and will happen with Drive in Genesis.

Yes, but what's important is that there is a way for them to get their power back that they can excuse any future appearances with. The same will likely be true of Takeru.

Well supposedly Specter isn't a Ghost though, so I'm not too sure that being one is actually a requirement of using the Driver at all.

Tendou also technically 'lost' his powers, but they could easily explain that the Kabuto zecter comes back for him if his assistance is needed.

As for Ryuki, maybe the Shinji Kido from Episode Final is the one constantly showing up, and not the one from the original timeline. I've always theorized that the Pre-Den-O movies are themselves A.R. worlds where Tsukasa can go and recruit Riders. It would certainly explain why Diend can summon riders that supposedly never existed.

Ah, I wasn't sure about Kabuto anymore since it's been so long since I watched it. But yeah, it's still Tendou, so the Kabuto Zecter will probably appear for plot convenience as everything in Kabuto did, lol.

The idea of A.R. Ryuki is pretty neat, tbh. That would actually make sense for once.

Adding to this discussion about Riders keeping powers, Eiji did get the Medals back in Mega Max, but he kept them after that. The thing up in the air on when he did it was bringing Ankh back. His cameo in Ultimatum...yeah, I just assumed he didn't need to transform to handle a couple of mooks.

Regarding Fourze, the Fourze Driver gets destroyed 5 years after Ultimatum, which makes it 2017. Meaning not until the Rider after Ghost has ended. Until then, Fourze's appearances make sense. And even then, Kengo outright said that the Fourze Driver will continue to appear to help Gentaro, even though it seems to be destroyed.

As for the other Neo-Heisei Riders so far, they all still have their power, whether full time (Double, Wizard, Gaim) or for emergencies (Drive).