If Sony said GT Sport is releasing this year, then it's the full game.
Maybe Sony decided they aren't doing a beta, but rather they're just releasing the game.
They've had betas for a bunch of other games, so server load could be anticipated by those metrics and adding the "Gran Turismo Factor", like you take whatever Uncharted is going to require and double that, because GT usually sells like a beast.
If there is a Beta then I would think it'll just be announced at E3 along with the release date.
Dreams is another game that is meant to have a Beta at some point, but Media Molecule haven't confirmed when that will happen yet.
One thing's for sure, Sony are going to have a lot of exclusive PS4 games to cover at E3, given what was announced for 2016 release already.
