I just found this trailer analysis by Trek Central. Looks like they going with post apocalypse (the controversial supernova event) Romulan's experimenting with Borg technology presumably to try and regain some lost power. Gotta love the lab sign saying 5,843 days without assimilation lol! Looks like they have control of a cube too. Considering Romulan's and Borg were my favourite villains from TNG this pleases me greatly.
Oooooh looks like Robert Picardo, the EMH Doctor from Voyager might be in Star Trek Picard too. God this show opens up so many cool things for not just TNG fans but Voyager and DS9 fans too!