Hitman 3 will be renamed Hitman World Of Assassination, and Hitman 1 and 2 will be delisted from sale. These changes are Io Interactive's solution to the currently messy process of buying Hitman games or working out what you already own. From January 26th, when these changes take effect, there will be just two Hitman packages for sale. This might mean that you're getting some existing content for free, and it will mean that future DLC purchases should cost less.
Previously, Hitman sequels could contain updated versions of levels from previous games, assuming you owned those previous games. Throw in DLC, then game and DLC bundles, then launch exclusivity on different storefronts, and working out what to buy just to efficiently get the new stuff you wanted was difficult.
As of Jan 26th, there will just be two Hitman products for sale, IO Interactive say. Hitman World Of Assassination, which includes all the levels from Hitman 1 and 2 and all Hitman 1's DLC for $70; and Hitman World Of Assassination Deluxe Edition, which bolts on Hitman 2 and 3's DLC for an additional $30.
Existing owners of Hitman 3 will be upgraded to Hitman World Of Assassination, which means you might come away owning levels from Hitman 1 and 2, or Hitman 1's DLC, that you previously lacked.
If you already own most Hitman stuff, you'll also be able to use "'complete the set' functionality" to pay $10 for any DLC you currently lack. So if you own the Hitman 2 Expansion Access Pass and the Hitman 3 Deluxe Pass, but not the Hitman 3 Seven Deadly Sins Collection, you'll be able to pick it up for $10. Previously it cost as much as $30. IO say that the 'complete the set' options "won’t be front and centre for new players", but will be "visible to those who might need them."
Likewise, if you already own Hitman 1 and 2 as separate products, you'll continue to be able to play them that way even after Hitman 3 morphs into the World Of Assassination. It's only new players that will no longer have the option to buy them separately.
The Hitsman are fantastic games, and it's good news that it will be easier for new players to hop onboard the series. It's also nice that the few odd fellows who bought Hitman 3 without first playing 1 and 2 will now get those previous games for free. That's a pretty good argument for buying Hitman 3 while it's on sale, so that you benefit from the switchover when January 26th rolls around.
The post describing these changes also notes that they're being made in part with "the Freelancer game mode in mind." Freelancer is Hitman's delayed roguelike mode, which is due sometime in 2023.