During the ongoing testing process (which was upgraded ahead of Nakamoto with additional tooling and personnel) core developers identified a handful of bugs that were important enough to address before a mainnet release to ensure a smooth experience. Developers have already addressed the bugs and are now preparing the new Release Candidate which is expected in the next 24-48 hours. As always, core developers are committed to rigorous testing, a process that will continue even after Nakamoto is fully live.
If the RC is ready in 24-48 hours, why select a block one week later?
Great question. If the chosen block was simply selected 24-48 hours later, that would leave almost not time for node providers to upgrade before Cycle 83. What was already a tight turnaround became even tighter. Coupling that with feedback from Stacking Pools and exchanges this week about wanting more time, the decision to push a week means that the chosen block falls right at the beginning of Cycle 83, meaning that if they want to have their pools ready for Cycle 84, they have a 2 week period (1 cycle) to do so. As it turns out, this is a big advantage over the 3-day turnaround pools had with the previous Instantiation block and also makes it much less likely Stackers will miss any cycles.