this ended up longer than I expected, but here goes...
With the anime appearance and DLC, I was sure something big was in store for them, but the last we've seen of 876 pro was Ryou as DLC a while ago. Knowing Scamco I doubt they'll let the cash cow go unmilked, but from what I've heard DS was really not successful. (didn't the lead of the project end up getting booted out of the company after Dearly Stars?) So they're probably hesitant.
I finally got to play DS a while back, and it's not a terrible game. I feel like most of faults come from the limitations of the DS itself. The story can get hokey at times, but the characters are likable. I ended up really liking Ai after actually playing as her, and I was sure I wouldn't like her. Eri still remains one of my favorite iM@S girls. The graphics are... what you'd expect from a DS game. My main problem with it was how it felt kind of... watered down? There weren't a lot of songs or costumes, which are my favorite part of the series, and auditions and gaining fans are nearly nonexistent. It feels like idolmaster lite, but it's more plot focused. It had a lot of potential, but when it came to gameplay it faltered a lot.
TL;DR I hope the 3DS and vita hold good things for 876 pro! DS was flawed but not unplayable and actually pretty fun, but I hope the girls [and boy] get a really good game. They deserve it and they have a sizable fan base.
For now, all we can do is hope, but I personally think they'll get a new game someday. Maybe one will be announced next week, maybe one will be announced in 4 years. They tend to announce the new games when the hype from the earlier major game dies down, and the ps3 idolmaster was released over a year ago. Then there's Shiny Festa, but that game seems more minor to me.
as an aside how cool would it be if they made a new dearly stars game and the CG idols were the rivals for that game