Back on track. It may have been theorized already, but, I think Data is just appearing in a dream. He looks to be wearing a First Contact era uniform and refers to Jean-Luc as "Captain." Picard was still a Captain when we last saw Data and as we saw in the first trailer, Picard was referred to as an Admiral. Interestingly, at the Picard panel, Spiner said Data will appear throughout the season several times in different ways. I have a weird feeling Picard is going to have some sort of recurring dream of him or "visions" of Data throughout the season.