I am sorry for what I'm sure you'll deem to be a very unhelpful answer, but the only way you can come up even with a wild guess is by doing the following:
- Learn the most difficult page of the piece to your satisfaction.
- Multiply the time taken to perfect that page by the number of pages
I will say that, for a given piece, you are likely to learn it more quickly if you're more experienced. How much more quickly? Well, here are a few things that will probably vary with it:
- Familiarity with the composer's other pieces
- Familiarity with other artists in the time period
- Sight-reading ability
- Memorization capacity
- Exactly where you'll have gone once you've "gotten there" (are you performing it for your family? A panel of professional pianists? critics? Simon Cowell? a room of tone-deaf mimes?)
- Practice schedule
In summary, I don't know of the existence of any such database. I'm sure that if it existed, you'd be able to draw some very interesting correlations and even come up with a fairly accurate model to answer your question. But over the internet, and especially with the information given, we can take a guess, and we might even get it right (I'm betting on 1 year if you're really really dedicated), but that guess will be nearly entirely baseless.
In response to your comment:
You are, broadly speaking, correct in your assertion that your technical skill will improve as you learn the piece. After all, you must have some minimum amount of skill to play a passage, and that skill wasn't there before. But technical skill isn't usually the limiting factor. A large part of learning music isn't building skill, but memorizing the music (I call this phase of learning the "what the hell note is that?" phase). After all, pressing keys is easy. Remembering which keys to press for the next 5 minutes of playing is hard. That's why I've been playing the piano for over 15 years, but it still takes me a good month of solid practice before I learn the notes to a new piece.
Of course, the notes alone don't make music; if it did, we'd listen to MIDI tracks instead of musicians. We need to polish it to sound musical. This phase, which I call the "this sounds like crap!" phase, is limited by your ears. You will always, always find something to improve on. No exceptions. How long you polish the piece depends on how good you want it to sound. If it's good enough, then you can just quit and move on to the next piece. For me, before I play a solo piece for any serious musician, I take almost a year to work on it. But that's me, with my practice schedule. Some professionals know exactly what they're doing; they'll learn the piece in half a week, and spend the other half getting it ready for their peers.
The reason professionals can do this faster isn't because they've played really really hard pieces. They can learn faster because they've played more pieces. Over their schooling alone, they'll have played hundreds of pieces of music, and over their lifetime, easily thousands. The quantity of music that you play will contribute to your composite skill far more than the difficulty of the pieces.
Which brings me back to my point. Learning a difficult piece isn't a trivial task. Memorizing the notes is. So if you're just memorizing the notes to bang out, then you're limited by how fast you can memorize. If you're going to polish it afterwards, then you're done whenever you're done polishing. Either way, it's not a question that we can answer.