It just struck me that this new story line with the NMLA makes a certain amount of sense.
Considering that Oddessy will be released eventually (soon?) along with the ability to land on planets and moons with atmosphere. It will no doubt include the option to have an opposing force to fight according to the pre release teasers. Of course like most factions civil war, power play etc, you'll have the option to take sides, do missions or simply pvp.
Perhaps, like the Thargoids, NMLA's base of operations /home world will also be a big mystery.
But like all plots in ED, there has to be a storyline to begin with; and I think that this new Rebel faction is a precursor in direct relation to the release of Oddessy.