Will there be a sonic 4

It is extremely unlikely that they will make a Sonic 4. Sega's focus has been more about unique adventures for sometime now that really have no bearing on Sonic himself. So for example the most recent games events have no storyline bearing on the next game that will be released. Sonic & Knuckles for the Genesis could be seen as #4 as it was canon plot and game to Sonic however it is not officially Sonic 4.