Im not sure how many. It has been confirmed there will be atleast 7 seasons. but I think it can go past that.
If Rugrats can go past 7 seasons, or even 10, Im sure Spongebob can. Spongebob is way more popular than Rugrats was.
Rugrats was good with the first 65 episodes and then it turned to soft warm turds, with Dil & Kimi. I just hope Spongebob or Sandy or someone doesnt have a kid to ruin the show. The Fairly Odd Parents have been ruined with Baby Poof.