Possibly the most anticipated update ever to be announced for GTA Online, Bikers, is launching tomorrow worldwide on PC, Xbox One and PS4. Surprisingly enough, we haven't gotten a trailer for the update yet, and very few details have been revealed. In past cases when major DLC packs were announced, Rockstar published a wealth of information ahead of launch.

Of course, there were cases where the given DLC was announced the same day it was released. With Bikers, however, we've got a major update much like Further Adventures in Finance and Felony as well as Executives and Other Criminals, both of which had quite a bit of run-up before release.
What we know so far about Bikers is that it will add a mechanic to GTA Online wherein players may form their own Motorcycle clubs with up to 8 members. As far as we know, these are independent of Crews, which are the equivalents of clans or guilds. The update will also be bringing new clothing items, weapons, tattoos and other character customization features as well.