I know its a little early but I just wanted to put some opinions out there
The first half of Season 4 I believe will be Rick's group tidying up the prison, securing its breached, repairing the gates and focusing on training the Woodbury citizens, as well as going out on runs to get food. they might, just might actually farm the Prison field like they said they would in the beginning of Season 3.
As for the Governor, I think he, Martinez, and Shupert will stumble upon a National Guard armory, there he will assemble a small army by enlisting survivors with the promise of a safe haven (the prison) and guns.
The Governor will probably strike in the last few episodes, with probably a dozen well armed, and hardened survivors, an intense shootout begins, and many on both sides are killed.