IO Interactive have been the sole developers of main-series Hitman games since the origin of the franchise. However, due to Eidos' purchase of IO and Square Enix' subsequent purchase of Eidos, the Hitman IP appears to belong to Square Enix at this time. It's not yet known what would occur with this IP in the case of a transfer of investment; my suspicions would be that it would be allowed to stay with IO if a new investor is found, or kept by Square Enix if one is not. Neither Square Enix nor IO Interactive have put forth any further details at this time.
Square Enix is expecting to take a single-time loss of roughly $43 million to divest from IO Interactive, which is obviously a very large number even for a company of their size. This appears to be an acceptable loss for the company, who commented that they are using the opportunity to "[focus] our resources and energies on key franchises and studios," which likely means reinvestment in Japanese studios and possibly Eidos Montreal? It's hard to tell where all they have active things ramping up these days.
Source: Polygon