If the update is a processor bump, and not much else, then no special event is needed. Rumor is that this is what will happen with the 9.7" iPP next week. They've done this before with the macbook lines, releasing an early spring version with slight updates and no announcements anywhere. Honestly if its something like that, or even something from the iPad 3 to the iPad 4, then no, I think an event solely for that would be ridiculous. However, if they are having a special event anyway for one of their new products or major refreshes, then it would only make sense to just announce the minor updates there and not have a silent refresh.
The events help a lot with the hype though. They make it sound exciting and a big deal when there really isnt much to awe about. Thats what happened with me and the WWDC last year. iOS 10 brought a lot of changes to messages... changes that really werent any value to me. Even with me not having any smart devices for home automation, I recognized that the new home center app (or whatever its called) was probably the best feature the update had to offer. But my point is, I think special events help introduce hype for even a minor update because apple's fan base is so strong.