Not an answer - just an observation...
The next event?
Only Apple knows - and they're not telling.
For the last couple of years, Apple tends to release updated products without a lot of fanfare, and when they are ready to release.
If you buy a new mini now - it's not going to suddenly expire when a new update is released. It will continue to be the tool that you purchased, and do the job that you want that mini to do. If a new model comes along, that has that new feature that is your new 'must-have', then you eBay the old one, and buy the new one - simple, eh?
If you wait to buy, then you'll end up disappointed because Apple 'forgot' that must-have thing that all the 'rumors' said was in the next update, and Apple (again) ignored your pet project...