https://wccftech.com/modern-warfare-2-could-come-back-to-steam-on-pc/

Call of Duty: Modern Warfare 2 could mark the franchise's return to Steam on the PC platform. That's at least what could be inferred by the fact that the game's artwork was spotted on the series' Steam page. While Activision Blizzard has since taken down the picture, it can still be found on Steam's CDN.

Obviously, it could be a simple mistake made by someone at Activision Blizzard. However, the company has agreed to be acquired by Microsoft (although the deal may still be blocked by regulatory agencies) earlier this year, and Microsoft has brought all of its games on Steam after attempting to release the titles only on the Microsoft Store.