Probably either Traditions of the Trade or A New Life.
Although I would rather they just did new levels.
Perhaps a few years after Hitman (2016) is completely finished, they could do a remaster of the best levels from previous games. Here's a few suggestions:
All Triad levels in one
Lee Hong Assassination
Traditions of the Trade
Anathema (don't know how to spell it)
St. Petersburg Stakeout
(Haven't played silent Assassin, just saying ones I think might be cool from what I've heard)
A New Life
You Better Watch Out
House of Cards
A Dance With the Devil