Let's speculate and say the announced X-Corps are X-Men teams in each region; North (Canada/Greenland), North-East (Russia /Poland/China), Far-East (Asia), South (Central and South Americas) and West (Europe). Each X-Corps has to have 7 to 8 members and they'll come originally from that region.
Here is how my 4 teams would look like:
NORTH
(Canada and Greenland)
Wolverine
Radius
Deadpool
Aurora
Northstar
Flex
Talisman
NORTH EAST
(Russia/ Poland/China)
Magneto
Colossus
Magik
Darkstar
Sibercat
Red Lotus
Jubilee
FAR EAST
(Asia)
Sunfire
Neal Shaara
Silhouette
Indra
Karma
Kwannon
Surge
Dust
SOUTH
(South and Central Americas)
Sunspot
Feral
Magma
Cece Reyes
Rictor
Darwin
Empath
Arclight
WEST
(Europe)
Nightcrawler
Psylocke
Banshee
Chamber
Black Tom
Wolfsbane
Pete Wisdom
Avalanche