just to be clear, I added the 60s style ships to the article on TrekMovie because I thought they were interesting. However, as has been pointed out, the USS Kelvin is as 'real' as a heart attack...just ask Captain Robau (if he doesn't kill you for even asking him).
The irony is that a TOS style Kelvin is actually less canon, since the Kelvin is from a generation before TOS (it was launched, in the Prime canon universe, before Kirk was born). It sits between ENT and TOS, kind of like the Enterprise C sits between the TOS movie era and TNG. So a TOS style Kelvin could only be a successor or refit of the original (and very canon) Kelvin we will see in the Star Trek movie.
So the OP is not 'canonizing' the
Kelvin, he is TOSing a
Kelvin (a different ship) and 'fanonizing' a history...and that is all