This forum somehow managed to find out about this. A follow-up to Sonic Runners called Sonic Runners Adventure, with Gameloft somehow being involved. Coming to Android and presumably iOS as well. EDIT: In case there was any doubt about this being real: it's been spotted on Gameloft's support site. Lots of details on there, but most importantly: the game isn't online only. EDIT 2: Gameloft took the page down, Sonic News Channel archived it though.