What SL63? It doesn't exist yet... rumour has it that the SL63 is not coming at all. Instead an SL69 (teehee) might be in the works. I don't remember where I saw that but the SL63 seems just as unlikely as the SLK63.
It's weird though that so many models have been upped from 55 to 63 but the poor 'flagship' SL hasn't gotten it.