Yes but in this case it seems that in his older years Kenobi's accent became more "core world/aristocratic" instead of less. It definitely didn't blend in with the way anybody else spoke on Tatooine.A friend of mine lived in Australia for two years, working as a nanny. She came back and had an accent.
Kenobi's accent in the PT was described as "Coruscanti" so I imagine him blending in with the locals will be all the explanation really needed.
Kor