Regardless of E.X. Troopers poor sales in Japan, Capcom has released 2 additional missions for absolutely nothing. The first mission was released earlier this week and forces you to fight every dongo (the roly-poly Akrid) type, plus 2 dongo gears (same Akrid, but has a mounted turret with a guy riding) at the end. The next mission pits you against most of the enemy types, but gives them absurdly high damage. These enemies also feature reduced health, so the mission is about killing your enemies fast, over being amazing at dodging.
No word on if there will be more missions in the future, but I suspect we will see a few more stages. Since E.X. Troopers uses unlocks via the server and not the Playstation Store, I made a quick guide to demonstrate how to download these missions.