Ever since SEGA went all out with Sonic Boom and it died in the ass, it's been pretty clear that they don't know what they're doing with the series and have no clear direction to take it in. They're throwing everything at the wall in an effort to see what sticks, and have almost completely lost touch with the wider gaming community. Mania was an enormous success, but it came out sandwiched between the middling Forces and a few years of total stagnation. Sonic was already struggling after well over a decade of questionable games, to such an extent that even Generations wasn't enough truly prop up the series. They were going for a bold new lease of life with Boom but (because SEGA can't be trusted to do anything right) it had an uphill battle from the start and was already a failed venture before it launched.
I don't feel like there's any clear indication of what SEGA want Sonic to be right now, and there's a huge disconnect where they clearly don't know what the audiences are looking or even which audiences to focus on. With the recent resurgence of two other 90s mascot platformers in Crash and Spyro and Mario back on full form (if you can even consider the Wii U years anything more than a slight stumble), Sonic is just flailing. The way that the series is being marketed and games clearly not being given the budget they were just a few years ago makes me wonder what could possibly be in store next.
If there's ever been a time for the franchise to take a break and lie-low whilst something new, fresh, impressive and relevant is cooked up, it's now. But that's obviously not going to happen with the movie out next year. SEGA can't afford to not have a game propping that up (whether that's a tie-in or just a regular game). I'd at least line to see them stick to smaller spin-off games of a really high quality (i.e. Mania and the Sumo racing series) for a couple of years whilst they work on a solid main 3D game to rejuvenate the franchise properly. You know, like what many of us were expecting Forces to be when it was first teased.