As an explanation to people unfamiliar with these games: If you treat each location as a single linear level then yes, you're going to find Hitman 2 and Hitman 2016 to be short games - but they're structured very differently from previous entries in the series. Each location is its own huge open world, with all the features and interconnections that that would imply. Each location has a "mastery meter" that you can fill up by doing challenges in each location (and you don't even need to do half the challenges to fill your mastery to max) that will unlock new gear for you to try out, sometimes exclusive to that location, sometimes not. Challenges can range from finding new ways to assassinate main targets, to finding certain Easter eggs, to finding various disguises... one level in Hitman 2016 gives you a special coin if you can complete a hidden coin-bouncing mini game in a fountain.
Add into this that IOI has added more than just the main missions in locations, such as the missions added by the Bonus Episode or the Patient Zero campaign, each with their own new set of challenges and a remix of their respective locations with different events and times of day going on, the Professional difficulty which throws numerous wrenches into your old strategies (but awards prestigious cosmetic unlocks if you can overcome them), and the user-generated content in Contracts mode, and one location on its own already has more content and replay value in it than all of Absolution. Long story short, I have like 200 hours in Hitman 2016, I just really like this game okay?
They haven't been super specific about it but the rumor is that they'll be releasing two more locations after Hitman 2's launch as DLC. If that's the case, I'm extremely hyped.