Well, these few days have been absolutely filled with surprises. Not only did it turn out that the Lowriders DLC for GTA Online is real, but most of the rumors that were circulating about it actually turned out to be true. This includes the ones about the new vehicles, the hydraulics, and the new missions courtesy of Lamar.
The DLC went live just today, giving players 1.4 GB worth of new content to play around with.

Now, Lowriders is quite the substantial update, and it will keep GTA Online fresh for a very long time. However it seems that counter to what every sign has been pointing to, Rockstar won't actually let the spookiest celebration of the year pass by without some more new content to celebrate it with.