I do not believe that this is a real GTA V Beta video. They are multiple reasons as to why. There is a few debug strings in the upper left corner, usually, the debug is disabled for the QA team in Beta. Only ones with access to a debug build in Beta is a developer and trust me, they don't want to lose their job by leaking stuff. The mini-map doesn't look as good as GTA IV's, unless it is still a placeholder of some kind. The van is a Chevrolet and not the usual van they use, that would be a May require legal approval issue, since they never used any real-world vehicle, due to licensing costs. Also, it doesn't have the same rear end as the one we see in the trailer, where the guys are disembarking from to commit a heist (@0:46). In the debug text, we can clearly read Grand Theft Auto Five, which is weird, most of the time they won't use something as clear as that in any file during development. For example: The Rainbow Six games (1-3) were named after US Generals, such as Eisenhower and Patton. Look at the type of font on the road sign on the left and it is a standard MS font.
The game was announced a little over a month IIRC, with no release date so far. I personally do not believe that it is in Beta stage right now, it may have been in Alpha when they announced it and probably is still, since games in open-world environment takes an extensive time to pass each steps (Pre-Alpha, Alpha, Beta and RC) by the QA, whether internal or external. The RC would most likely take about a month in such a game, so if they are aiming for a June or July release, they would still be in Alpha right now, if not a step prior.
Let's say that they want to release it in mid-July, they would have to have a stable RC that would be submitted to Microsoft and Sony for approval at least a month prior to the release date. So that would place the submission to maximum mid-June. RC stage to last a month,starts around mid-May and let's say 2 months in Beta (which is very probable in an open-world game), now places us to the beginning of BETA in mid-March.
Also, it is easy to do trailers for a developer, since they don't have to show everything but bits of the final product.