Courtesy of commenter "RJ", according to Robert Herjavec's Twitter account there will be more Shark Tank:
Great news - ABC has ordered more episodes of Shark Tank !!!! No air date yet - but it's coming.
Robert's Twitter account isn't a verified account, but it seems legitimate enough, and this isn't something I'm going to try and get confirmed over the weekend. Shark Tank wasn't exactly a ratings juggernaut, averaging a 1.7 (blended Live+7/Live+SD results) adults 18-49 rating for the episodes after September 21. But Shark Tank did have some critical acclaim and it could be that the show also has a higher percentage of high income viewing relative to other shows, and apparently the foreign versions of the show (like Dragon's Den in Canada) were slow ratings starters.