It would be best to plan for at least a three year hold on domain names. Normally, it can take five years before a new TLD stabilises in terms of development and registration patterns but the third year is where a lot of the highly speculative registrations have been cleaned out. There will be a Junk Dump around this time next year of domain names that couldn't be sold or developed. It always happens. But there are ongoing deletions as the .UK has been around since 2014. I'd have to do a few queries on the databases to see which ones were deleting but some of the domain names in the 01 July zone were on deletion/renewal nameservers.Yes, there are lots of unknowns. I would guess in a year to 18 months we should have a good feel of where we're headed with .uk!
Regards...jmcc