There may be 80,000 on the mailing list, and 10,000 here. But my guess is that many of those will not order from the first batch, having lost interest, found something else, not have ready funds etc.
I think the first batch will sell quickly, but a significant fraction of those wanting to order will be able to.
I hope production can be scaled up quickly, because if the foundation only has enough money to order this first batch, it is not going to be quick. Based on Liz's blog post a while ago, the profit from each board is less than 25% of the production cost, and since it seems to take a month from placing the order to getting the boards to sell:
1st March: 10,000 boards
1st April: 13,000 boards
1st May: 18,000 boards
1st June: 24,000 boards
1st July: 32,000 boards
1st August: 42,000 boards
1st September: 56,000 boards
Which means it will be July before 80,000 orders are shipped, and that ignores other calls on the foundation's funds, such as building a support structure.
Even at that slow rate, it should be possible to have a credible capacity by September, which must be the important deadline. I hope that there are other funds available to allow a faster ramp, but 10,000 boards costs somewhere around £170,000. If the foundation is to put an order in for 100,000 boards they need to find a couple of million quid from somewhere.