Dataminers found in the Call of Duty: Modern Warfare files of 23 new game modes.

Some of them managed to find a description:

Team Juggernaut. Each team has a juggernaut. For his murder, the team gets additional points. The winner is the one who gets the maximum points.

Reinforce. You need to capture the points to revive the timepieces. The team that has captured all the points wins.

Rupture. You must take control of the powerful juggernaut and capture the enemy base.

Infected. The dead turn into infected. To win, you need to infect everyone.

High-Value Target. Killing enemies gives us points. If you kill a more valuable opponent, you can get your points back.

Gun Game. To win, you need to kill the enemy with each weapon you provide.

Grind. Collect tokens and take them to a point to win.

Drop Zone. Hold the location to get points and a valuable load.

Demolition. Teams take turns attacking and defending points.

Defender. Capture the drone and download the data to get victory points.

Search and Rescue. Teams take turns defending and attacking targets. Tagging bans players’ respawns.

Capture the Flag. Capture the Flag on the enemy base and take it to your respawn.

Fire Mission (+ Hardcore). Destroy the enemy, grab the base and take out the VIP to win.

Assault. Attackers try to capture the bomb site, the other team protects it.

All or Nothing. Players appear with a throwing knife and a pistol without bullets. Perks are given for kills, but disappear after death.

Other modes description could not be found:

Showdown (+ Hardcore)

Onslaught

Incursion

Fireteam

Breach

Arms Race

It is not known whether at least one of these modes will appear in the game or it is just the remains of the test code.

Call of Duty: Modern Warfare was released on October 25th, 2019, and was the restart of the Modern Warfare series, not its continuation.