PS3 to PS4

[Felis]

I think your account gets upgraded to PS4 in that you can't play PS3 anymore. Which could be a problem if your PS4 ever broke although unlikly

i'm sure it would be still possible to re-register the PS3 version with a new copy

The Live Letter this weekend will be about the PS4 version?

Maybe, if there is something new. They already showed the PS4 version in the last live letter.
The main theme of the coming live letter is 2.2