The build up at this point is just too strong, so there is a ton of convincing evidence that in fact both will die. The only thing I truly accept as "going to happen" in that big theory/spoiler thing is the fact that Luffy will in fact end up dying against either Kaido or some other big bad in the next couple of arcs, and Law will revive him by sacrificing himself and using the Ope Ope fruit to give Luffy limited immortality (i.e Lifespan only. He will still be able to physically die if killed for example, but he wont die of natural causes.)

It just makes too much sense, and quite honestly sets up an ending for One Piece that I truly believe is worthy of Oda envisioning from the getgo.

Picture this. The final chapter of One Piece opens up with a page depicting a time several centuries into the future, a cloaked figure wearing a straw hat sitting surrounded by a group of enthralled children and their parents. It's a teary eyed Luffy finishing the telling of his tale, sad at the fact that he alone is alive while everyone he once adventured with is long dead, but also happy at the fact that they truly did achieve each of their dreams.

Of course, I think Oda would write and draw something like that in a much better way, but as cliche as it might seem to some, I can't really think of a better ending to such a long and incredible series.