Paul Gadzikowski

When the Doctor told Sarah Jane in School Reunion that he'd regenerated "half a dozen times" since they'd last met, he was using an idiom that doesn't always mean "precisely six". It does not mean that The Five Doctors never happened, and it does not mean that there can't have been incarnations we don't know about between the Eye of Harmony thing and the London Eye thing.

Even if the Doctor did mean "precisely six", that doesn't mean The Five Doctors never happened. It was obvious then that Sarah Jane didn't realize Doctor Five was the Doctor. He probably thinks she never figured it out (though he's probably wrong).

If there were two incarnations between the Eyes, it'd mean Pete's Doctor probably is the Valeyard.