I'm not sure if this is a comprehensive answer, maybe it's more of a personal opinion, but I'd ask what's the goal?
Are you trying to reduce boiler plate/amount of code you need to write? Then I'm afraid it'll be the same if not more, since you'll have to go to every activity and add the inheritance part.
The downside to me is that you're now using inheritance to implement something that was avoiding it. Annotations give you the opportunity to annotate any activity without saying it's a base activity. This is often better than inheritance since not every activity is a base activity and you decouple your code more from what dagger is actually doing. I think this is more of a delegate pattern or maybe more like a decorator.
That said, to answer your question, I'm not 100% this works, but to me it has the downsides of using inheritance for something that should not be modelled by inheritance.