I think he probably will turn out to be the final antagonist of the series.
I seriously doubt he's going to lose this battle, although I'd wager he'd be somewhat weakened by it. If everything goes according to plan, and I think it will - what's the point of ever Kishimoto ever mentioning the moon-eye plan, etc, if we'll never end up seeing it - then he will definitely be the strongest. At the moment I'd say he has the most potential for being the most powerful. We've only see a fraction of Kabuto's and Edo-madara's abilities so far (and I'm not sure if you really count an edo-summon). personally, I would be disappointed if Kabuto turned out to be more powerful.