TNG established that Picard grew up in a vinyard. Him retiring from starfleet and returning to his vinyard...makes sense. For the show to feature the vinyard as a plot device or recurring element may be....unwise.
Yes, it is my opinion, even based on the scant information, that people who think they are cadet uniforms are wrong. If I am proven wrong when the show comes out, so be it.
Let's try and break it down.
1. Picard is - apparently - returning to active duty (unclear if he will be a civilian at this point, his lack of a uniform certainly suggests that)
2. The colored uniforms are seen at what is clearly meant to be a starfleet location on earth, most likely Starfleet Headquarters or Academy.
4. The prevalence of young adults wearing these outfits is certainly suggestive of them being cadets
5. In the background of a couple of these stills it's there are a couple of individuals wearing what
appears to be the Nemesis uniform - suggesting again that the brightly colored outfits are cadets.
6. The last Star Trek episode to feature cadets was DS9 Valiant, where the cadets wore gray jumpsuits with colored shoulders, while officers wore black jumpsuits with gray shoulders and colored turtlenecks.
In Conclusion, it's highly
suggestive - by no means
conclusive - that these new outfits are meant to be academy uniforms.
Other likely possibilities are that these are line officer uniforms, or that these are meant to be "background" costumes worn by extras and that "hero costumes" for the main actors are going to be similar but more finely detailed.
There is certainly more than enough evidence and speculation at this point for it go either way.