Coming from an interview with Sonic Team...
We at Sonic Team – are developing a completely new game, as well as developing a full movie, actively done by Sony Pictures, and animation on Sonic Boom. We are also ready to improve sponsor ties. The most important thing is not the fact the series survived for 25 years, but how many games was developed. Our goal – add something new and overcome any potential hardships.
Now let's just hope that the game comes Nintendo's way and is also worth the wait. Sonic deserves something truly great for his 25 years of hard work!