I would hate for that to be the case. It would also be too cliché. It would cheapen it to me if he were to find One Piece then die. Sadly, you're probably right though.I think it'll be even worse than that. Luffy's lifespan being shortened has been something Oda's hinted at for ages, ever since Gear 2nd.
My guess is, after this fight, we'll find out Luffy is dying and only has X number of months to live. So it'll be a race to find the One Piece before Luffy runs out of time.