Last year the registration announcement was in mid November. I expect for this years announcement in late October mid November this year, so be patient.
Our team usually calculate a mid April launch window for GSBC so we could start the rough timeline planning early and make smaller adjustments later as the exact launch window is known. I could suggest this for everyone. Prepare your team for an early April launch date, schedule your last tests on the end of March and you could be fully prepared for the official GSBC launch window.
As far as I see the 'Challenges' and payload requirements are usually the same, so you can prepare your experiment and development prior to the announcements. Tracking system and camera are usually the main requirements so this could be the base of the development. So you can start by determining the specifications of the payload and experiments by last years 'Challenges', leave open some parameters for later clarification and adjustments. If you study the last GSBC announcements and requirements you couldn't make major mistakes.