Is TeamSpeak 2 compatible with TeamSpeak 3?

TeamSpeak 2 is in no way compatible with TeamSpeak 3. Keep in mind TeamSpeak 3 has been completely re-written in C++, introduces new features, and the protocol itself has been completely re-engineered. Therefore, you cannot connect to a TeamSpeak 3 server using a TeamSpeak 2 client, nor can you connect to a TeamSpeak 2 server using a TeamSpeak 3 client.