Well, the digital pianos, and if I remember right, the P80 is fairly newer, the ones they make now sound like a real piano. Hard to tell the difference aside from the sound coming out of speakers instead of the piano itself.
If it has MIDI hookups, then yes, you can use it for quite some time for the future, until some random huge CEO decides MIDI is outdated and everything goes to shit. But let's save that discussion for another day
Anyway, you're fine. I think I played a P80 once and it was very, very nice. You seem way serious about realistic piano action, so definitely stay away from 'semi-weighted' and synth action keys, you're probably not gonna like either of those options. It's almost like you want them to stick or something XD but play around with the P80 for a bit more and see if it's really worth all that money. Also, I would only get a midi controller if I wanted some extra, mappable keys.