They only announced it with actual Arena seasons involved, bear in mind that the Classic PvP System isn't something you can just grab all the rewards in a few weeks.
If you want to go for R14, you're in for a 3 month grind at minimum.
It's simply not reasonable to expect an actually useful announcement when it comes to the Classic PvP system, if you aren't already close to your desired rank, your chances of getting one of the higher ranks are pretty low.
Bear in mind, in a regular Arena season, you also need to deal with rating decay / inflation, if you played at the start of a Arena and then stopped, the announcement gives you a chance to get back your previous spot / a frame where you need to play if you want to get Rank one, rather than play every week in fear a patch might hit soon.
If you didn't rank in Classic until TBC is already on the horizon, you just couldn't be arsed to rank in over a year.