Modern Warfare is likely the most popular in all Call of Duty series and if the latest rumours turn out to be true, Activision will attempt to milk the titles intensely as four new MWs are apparently planned.
Call of Duty: Modern Warfare turned out to be extremely successful both with the original from 2007 and the reboot in 2019. The original had two sequels while the reboot might be going much farther than that.
According to The Gaming Revolution , it was leaked that four Modern Warfare games are planned in the future. It appears that the goal is to build character stories as each game takes down one of the four horsemen. As a reminder, the horsemen in the original run were Imran Zakhaev, Victor Zakhaev, Khaled Al-Asad and Vladimir Makarov.
There is a mention of Zakhaev Jr. in the epilogue of Modern Warfare (2019) so these claims definitely have some truth to them but just because one detail turned out correct does not mean others are too. Therefore, it would be a good idea to take the leaks with a grain of salt for the moment, until official news from Activision come.
In a followup to the leak about four Modern Warfares, The Gaming Revolution also mentioned that CoD: Modern Warfare 2 Remastered multiplayer is still in the works and might happen in the future. However, there is suspicion that this could be a test to see the community reaction and TGR is well aware of that possibility.
Regarding the source of leaks published by TGR, this is the same person that initially provided info on the battle royale that eventually became Warzone.