In the New Skool vs Old Skool trailer, I'm not certain but I figured someone on this sub would know if it's Old Raiden and Scorpion, with New Sub-Zero and Jax? :
NetherRealm Studios Release New Trailer Showcases Mortal Kombat 11 Old Skool vs. New Skool - Gameranx
Liu Kang, Kung Lao, and Others Revealed in Mortal Kombat 11 'Old Skool vs. New Skool' Trailer - Total Gaming Network
Mortal Kombat 11 "Old Skool Vs. New Skool" trailer