A bit over a month after the collection got to 4000 items, my collection sorting Illustrious models for "western" girls has finally surpassed its Pony predecessor with 4379 to 4378 models collected. This has made it the fourth largest model collection (by item count). I'm pretty confident I'll never be in the top three though.
This isn't to say Illustrious has only now surpassed Pony in general usage. I think it achieved that roughly 9 months ago as usage rates for my Illustrious versions of my models have begun to far eclipse their Pony counterparts (I had converted my stuff to Illustrious by Feb 18 2025), and Pony usage for most models had cratered. From my usage reports, I can say these days only one series of my models see any significant use of the Pony versions (couldn't say with confidence why, other than that series being very popular in general, with the Illustrious version my top earner) and its been that way for some time. I suspect Pony kept getting significant new model support (making it harder for Illustrious to catch up as so many preserved the current gap) long after usage had stopped because it was easy/cheap to support for creators already making Illustrious models (With the dataset already saved, it literally takes longer to setup the page for the finished model than to setup an extra training session for it, especially if time for setting up sample image prompt setup isn't counted) and nobody really had catalyst to abandon it despite falling interest as a result. I certainly only decided to stop when a bug briefly increased LoRA training costs with the on-site trainer and decided I wouldn't bother converting unless explicitly requested. While that bug was fixed and cost returned to 500 buzz, I only ever got one conversion request since so no reason to go back.
As I mentioned when it hit 4k items, I originally started the SD1.5 version to sort models for my own purposes since there so few models of them back in the day, then made the "mistake" of starting versions for Pony and Illustrious (also Flux and video models, but those haven't really gotten much use). Never expected these would become some of the site's biggest collections. I certainly am not going to do a ZIT version (but feel free to if you want), especially since further features for collections never really materialized.
Edit: I'm going to be hitting 4k followers (3915 current) and 200th "unique" LoRA (at 196 LoRAs. Currently doing work on cleaning images for my 200th, which will be my second largest LoRA ever. Numbers 197, 198, and 199 also WIP.) relatively soon. Lots of milestones happening for me.