According to Activision's Bobby Kotick and Thomas Tippl, the 2017 release of Call of Duty will bring the series "back to its roots" in terms of combat.
"In 2017, Activision will take Call of Duty back to its roots and traditional combat will once again take center stage," Tippl said.

"This is what our dedicated community of Call of Duty players and Sledgehammer Games, which has been developing this year's title, are the most excited about."

Activision feels as though the lackluster sales (at least compared to older games in the franchise) of Infinite Warfare were due to the drastic change in setting.
"It's clear that, for a portion of our audience, the space setting just didn't resonate," Tippl stated.

"We have a passionate, experienced studio deeply committed to this direction, and despite the risks we saw, we believe it is important to consider the passions of our game teams in deciding what content to create."

It's a bit odd to say that though, because these games are usually on three year development cycles spread out between Sledgehammer Games, who is working on this year's game, Infinity Ward, who made Infinite Warfare, and Treyarch. Given that, it means that the decision to shift back to the franchise's "roots" probably didn't come largely due to the lackluster sales of Infinite Warfare, a game released less than a year ago. Instead, it could have been a move that has been planned for quite some time. The stellar reception for Battlefield 1's WWI setting may have also played a major role in this shift in direction. This is, of course, merely speculation on our part.