Yep, 4 weeks. Next week plus three weeks in May for this challenge. That is plenty of time to get a head start on those summer goals before the next challenge.
The Between the BLs Challenge for Summer 2010 will be 5/28-8/27.
I don't know when the BL 10 show or challenge starts. It is like a state secret trying to get dates for the BL show -- that is why this challenge was extended twice, we have to kind of guess when we are in the planning process. Some times our guesses are not as good as we would like.

I imagine the BL 10 challenge will start 9/3 or 9/10 -- most of the time our participants don't want more than a week between challenges. The show will probably start 9/7 or 9/14.
Around the first week of May I will post the Between the BLs poll thread. This is where we post the dates, ask for coach volunteers, and take votes on whether we are doing one thread or teams. We also ask for suggestions about the challenge at that time. That is how we added our maintainer component to the BL challenge. It is also why we worry less about the BL show dates and keep the challenges going without a long break, it's what the participants asked for. We really do try our best to do what the majority of our participants tell us they want in a challenge like this and it has evolved over the years from what it was originally (which was before my time on the WISH boards). I don't start the planning poll until closer to the new challenge start because I don't like to take away from the existing challenge.
A big thank you to LuvBaloo who takes care of our weightkeeping duties and to donac, our COWkeeper. We couldn't do a challenge without them and all of you who volunteer to coach, participate and keep our conversation going.
Feel free to PM any of us if you have any questions or suggestions.