I know it looks like a death knell, but really what he's saying is that is that at least Adult Swim's involvement/financing for a second season was paused. They don't own the property, though, nor the studio that made the anime. Shit, they didn't even get merchandising in the deal. It seems like what they got for their part was limited broadcasting rights to the English dub.
I'm grateful to all parties involved for their contributions to the project, but Sega owns the property, and should be able to move forward if they saw fit. That's a big if, but my secret wish is that the anime did well enough in Japan that Sega sees it as something to supplement their burgeoning multimedia portfolio, and hands the anime over to Gonzo or Production I.G., with a real fucking director(!).
I honestly felt Shenmue deserved better, despite TMS probably doing some of their best work on Shenmue. It does hurt to read that tweet, though. Both for Demarco/Adult Swim family, and as a fan of Shenmue. Just don't throw dirt on it yet.