Or Picard never left the Nexus, and he's just imagining everything that's happened afterwards - since having more space adventure was his dream.
This has always been my thought, action hero Picard from the rest of the movies makes sense.
First Contact is Picard living out his history hobby by 'meeting' Cochrane, and dealing with his Borg guilt issues, Insurrection is just a convoluted build-up to having a love-in, and Nemesis is simply a bit of introspection, loosely following on from TNG Tapestry.
So Data never died then, and he eventually retired from Starfleet and lectured at Cambridge.
I must admit that I don't particularly like Generations, because I consider the Nexus too much of an 'unbelievable' plot device (it's too perfect and totally unnecessary). They could have done the same thing with the Guardian of Forever, or even Q instead to bring the two captains together.