Grounding's website has been quiet for the past three years - but only in English. The Japanese site reveals that they've been making board/tabletop games and, apparently, a Space Channel 5 VR thing.
Outside of that, I remember hearing about Futatsugi being credited in some mobile games, though I can't recall which ones.
Yeah I'm looking through their "products" page and their releases look something like:
Crimson Dragon for Xbox One, released 11/22/2013
"Gotouchi Tetsudou" for Wii U/3DS, released 11/27/2014
Mobile game #1 for Android/iOS, released 1/28/2016
Mobile game #2 for Android/iOS, released 8/8/2016
And that's all I'm seeing outside the Space Channel 9 and board game stuff.
Going by the credits for Crimson Dragon, they aren't a large team, maybe 30-50 people? Makes you wonder what was going on in the two years between the Wii U title and the mobile games.
At least the fact they are working with the SC9 IP means they must have some sort of a relationship with Sega, so hopefully we see more out of that.