I received this answer from Jolla by email just now when asking how long I will be able to pre-order?:

Hello!
Thank you for your interest in Jolla!
The end of the pre-order campaign has not yet been published. So please stay tuned!
We hope to see your order soon!
Sincerely,
Jolla Customer Care

It's not really saying anything but I thought I should share it either way Maybe I should have asked when they will publish how long the preorder will last instead. I've already ordered so it's not that important for me any longer...but I want that t-shirt!