The first pieces of information about Sonic 4: Episode 2 have been divulged by Sonic's brand manager, Ken Balough, on the official SEGA forums.
When speaking to fans about the reception of Sonic 4: Episode 1, Ken said: "I certainly cannot deny there were some elements that could have been done better "“ and I could say that about most games I've worked on."
To further this, he then went on to talk briefly about Sonic 4: Episode 2, as he stated that "SoA and SoE are both giving feedback and input on Episode II." He admitted that Episode 2 will give them the opportunity to address many of the concerns people had with Episode 1.
Hopefully Sega can sort out the weird physics that were present throughout the game. If they can, many of the franchise's older fans will certainly be satisfied.
Source: Sonic Stadium