Well, we're currently on our 4th week of rep gain, the time between cata release and the server restarts was enough time for some people to hit 500/6k into friendly.
And for the math part. For guild levels 1-25 you need 845,670,000 exp. You gain 6.246m exp per day. This means guilds will hit 25 on the 136th day.
From 0/3k neutral to exalted is 42k rep. With 3.5k rep per week it will take exactly 12 weeks assuming you hit the cap weekly. And I lied. On the 84th day people will hit exalted. My bad, I knew it was February and thought that was both, but when I redid my math only the rep will hit exalted in February, level 25 will be sometime in March or April it looks like.