Part of me is holding out hope that there's some ethics at play and/or since they'll likely be bringing over many of the same characters (I'm sure even the new characters since their story isn't complete like Alejandro and Valeria), that maybe it's much easier work NOT to remove all the skins.
But this is Activision and
My ideal hope would be,
We keep all the currents.
141, Roze, Alejandro, Valeria, etc.
buy MW3 and now in addition to those
Makarov
Yuri
Nicholai
Roach
Sgt Foley (Keith David)
Rameriz
Sandman
Griggs
handful of MW19 operators that haven't returned but are likely
Mara
Domino
Mace
Charly
Thorn
Lastly throw in some new 141 skins either from the new campaign or inspired by OG MW2-MW3.
SAS(Wolcroft) skin for Ghost
Classic, prisoner or Juggernaut for Price
Brazil, Cliffhanger, or MW3 skins for Soap
or Classic MW2 141 skins for everyone besides Ghost who already got one