Yeah Spidey, I see this discussion on a lot of other sites, mainly about sanctioned play. At first, RRR, you only have the option of the four guilds (WG, GB, UB, WR) so if you want to play UW it will be pretty annoying, but not impossible. Though you will be dead in the water to a strong guild deck.
Once Guildpact the next set comes out, it will be RRG. So you're still strong in the four main guilds, and the new three will get minimal support. You should be able to make a bridge guild to make a third color and go strong. THis may take some fancy setup in the first packs, though. For example, you may have to dedicate to both RW and WG if Guildpact happens to have a RG guild, for example, and you want to play it. Otherwise, you're as dead as the UW player in the RRR days.
The third set (forget the name) will shake things up as all ten guilds come out, but as drafters know a lot of your setups is based on the first pack. So you dedicate to a color or two colors in the first pack with the four guilds. A problem arises since Ravnica has four guilds. Four...um...while the others have three each. This means your Ravnica pack will be the weakest foundation for any chosen guild, but is the only way to get a foundation set up.
Hetemti's right, it will be a high reward setup for the draft-savvy. It all sounds like IPA, but with a boatload more strategy and planning involved.