Besides the main force marooned in Azys Lla due to Ysayle-as-Shiva freezing the Gration's engines and disabling the airship permenantly, a smaller unit of the VIth legion remains also stuck in the Sea of Clouds where they've established a rudimentary encampment right in the heart of Vanu territory (presumedly they were the accompanying force Varis and Regula sent to attack the Vanu and which were accidentally left behind when Regula and Varis had to do a hasty retreat back to the Gration when Lucia showed up in her magitek armour with guns blazing. Now they're constantly being hassled by the Vanu (there's a FATE there which shows them battling the beastmen).

As for the VIIth, the original legion under Eulla-as-Nael van Darnus were mostly wiped out during the Battle of Cartenau (as they were basically zealots completely and fanatically obssessed with carrying out the will of their late Legatus so they basically fought to the death. Any survivors that managed to avoid being killed or incinerated by Bahamut ended up being absorbed into the XIVth as I understand it, so the legion was rendered completely extinct, until now of course.