Craig Fairbrass, the voice actor of Gaz in MW1, Ghost in MW2, and Walcroft in MW3, has seemingly leaked Modern Warfare 4 on his Twitter bio.
Considering the CoD cycle goes Sledgehammer > Treyarch > Infinity Ward and Treyarch is releasing Black Ops 4 in 2018, that would mean Infinity Ward is making Modern Warfare 4, same as every previous MW game. Infinity Ward has had a shaky history since losing studio heads Jason West and Vince Zampella and nearly half of the developers at the studio in 2010. Modern Warfare 3 was fairly well received (though generally considered to be worse than MW1 and MW2), while CoD Ghosts and CoD Infinite Warfare are probably the two worst received CoD games to date. Can Infinity Ward redeem themselves with a 4th Modern Warfare game in 2019? At the very least, it's bound to have a better reception than Infinite Warfare I think.