According to a report from Nikkei Asia, it seems that due to the global chip shortage, it is said to have affected the production for some of Apple’s products such as iPads and MacBooks. If these products have had their production delayed due to component shortages, it is also possible that Apple might be holding off from making an announcement yet, especially if they won’t be able to deliver their products in a timely manner.
For the most part, Apple usually makes their products available on the day of announcement or a couple of weeks later, so maybe this production delay is big enough where it could force Apple to push back the announcement until they can get a handle on production.
Interestingly enough, the report claims that this chip shortage doesn’t seem to have affected the iPhone which is said to still be on track, although the report does cite a source who claims that supply is “quite tight”.