IO Interactive had previously promised that owners of Hitman and Hitman 2 would be able to re-experience the levels from those games from within Hitman 3, as long as you already owned them - but it seems, thanks to it's Epic Games Store exclusivity, that will no longer be the case if you own the games on Steam, at least for now.
Instead, players will now need to buy access packs to get the old levels in the game if you own them on Steam. Hitman 2 is only available on Steam, and never released on Epic Games Store, so in any event, you won't be getting those levels on the Epic Games Store version.
Instead, IO is trying to quell concerns by giving access to all of these levels for free as long as you pre-order the game or buy it within 10 days of release. If you happen to own Hitman on the Epic Games Store too, then you'll still get those levels for free regardless as originally promised.
On the upside, you'll still be able to import your progress from Hitman 2's Steam version, but you'll need to go through an import process on the IOI website, it won't happen automatically.
Hitman 3 is set to release as an EGS exclusive on the 20th of January.