Yeah, I'm with EC in that I'm pretty sure this won't be a First Contact War scenario. They might've gone with 'First Contact' in the title if that was the case.
We're apparently getting new alien species, so I'm pretty sure it'll be taking place 200+ years into the future. Whether or not they embrace one of the endings as canon, I'm not sure: maybe it'll use a Dragon Age Keep system where you can construct a savefile and the game will take some decisions into account, and make little changes accordingly. Honestly, the only endings that would be hard to implement would be Synthesis and Rejection: if the player chose Destroy you can have some throwaway lines about Shepard potentially having survived, and if the player chose Control you can have some exposition on how the Reapers departed the known galaxy after helping it rebuild. The geth wouldn't get a large role either way, but that's fine. The game simply wouldn't allow you to import a save with the Rejection ending (or allow you to create one), same as how Mass Effect 3 won't import ME2 saves in which Shepard dies.
I'm guessing the 'Contact" will refer to something else: something hidden in our galaxy for a long time, or something coming from outside our galaxy wanting to conquer new domain now that the Reapers are no longer around. Maybe those 'beings of light' hidden in Klencory turn out to be real after all.
I wonder if they'll try and work in the "synthetics will always destroy organics"-bullcrap again, or if they'll try their hand at the Element Zero plotline that was hinted at in ME2.
I hope we finally get to meet the raloi. Big sentient birds, it'd be like planet of the parrots. Too bad they got bird flu and then shut themselves off from the galaxy when the Reapers came.
I hope we get a lot more character customization options: after all the cool shit that was in the multiplayer of ME3, I'd love it if they implemented some of those powers. BIOTIC LASH, MOTHERFUCKERS.