I feel late answering this question, but I cannot answer this सवाल to the fullest; only provide information on how an ऐनीमे is made.
The first step for an ऐनीमे is how far the मांगा goes. If the ऐनीमे passes the manga, then the production cannot continue producing the ऐनीमे until the मांगा catches up. I know that the ऐनीमे isn't passed the manga, but for future reference.
The सेकंड step is money. If the producers reach the amount of sells required (6,000 units sold), then another season may be produced. Season one and the OVA season both exceeded the amount of sells needed, so season two was made. Season two feel short, but season one AND the OVA season could carry it.
The final step is public demand. If the public wants another season, they have the rights to demand for one. This step is dependent to the सेकंड step, however. If the producers cannot spare the funds for another season, then there will not be another season for whatever ऐनीमे the public wants.
There is another minor factor, and that factor is if the producers are working on और anime. Silver Link is in fact working on a few other anime, so they had to (temporary) drop Baka and Test, to get the other ऐनीमे going.
