No cheats in Black and White?! That's good news because I don't like cheated pokemon.
For the upgrade: I think we can only wait and see, even if it's funny to speculate.
I just tried to set my DS clock to 24 december 2010 but Arceus was still the last one. Perhaps it's like the migration from the GBA games: it doesn't depend on the clock. Perhaps the upgrade is unlocked via Wi-Fi?
Press sig to come to my trade shop!
Sig and Avatar by: Me