Like a said if pikachu were to evolve if at all it be at the very end of the series either the 2nd to final episode or the long awaited finale its self. But I'm sure he'll evolve when pokemon has ended.Uh, No, it isn't. Pikachu isn't going to evolve. The writers would never do that.
but wasn't there also a rivalry between Paul's Gliscor and Ash's Gligar? yet Ash's gligar still evolved.I don't think he will ever get a Servine. There always needs to be the conflict with Trip's Servine. But even if Ash does get a Servine, he won't get a Serperior.