I agree with the points raised by amirp about essentially .xyz (and many other new gTLD) numbers meaning relatively little - when they are priced too low for initial regs lots of people register them without being too serious (OK I've done that!), then a year later, surprise, they don't get renewed now price is high, and numbers go down.
I really wish we could get some stability in the registration/renew prices of new gTLDs. I think they need to have stable buy and renew prices that are slightly lower than .com. Maybe a blanket $5/year or something like that The premium renew prices just add uncertainty and in my opinion should disappear. If they want to hold some at higher initial sales prices, fine, but don't tack on differential renew prices for different names.
I think more meaningful measures of whether a new gTLD is having success:
(a) Are they actually being used by businesses/organizations?
(b) Is general public knowledge, trust and acceptance growing for the new gTLDs (including cc ones for general use)?
(c) Are they fetching at least somewhat reasonable prices on the resale market?
(d) Are they finding new uses, such as domain name phrases for marketing campaigns?
I would also like some way of enforcing that a TLD should reflect what you actually are (e.g. .com only if a real business, .science if it has something to do with science, .org if you are really an organization), but that is a dream rant I know!
Thanks for listening, and thanks to everyone contributing to the discussion!
Bob