The WWE went through a short period where they struggled with a lack of talent because key superstars, like Batista, left the company. However, recently there has been a good surge in young talent that has given the company more angles to work with.
Since his departure, Batista has been running his mouth about his dislike in the direction of the company. If the WWE finally moves away from the "PG Era," they might be able to get Batista to return (not sure if they want him to).
His last heel run before he left was arguably his best stint with the company. If he returns, he could return as a heel and use the angle of him badmouthing the company.