https://www.cnet.com/news/apple-store-down-ahead-of-iphone-event-2018/

Apple took its online store offline on Wednesday ahead of its annual iPhone unveiling bonanza at Apple Park in Cupertino, California.

It's common practice for Apple to pull the store down ahead of major media events, and when it pops back up it always features any new products the company has just announced. It also helps to build anticipation and excitement for what's to come, which in this case could be new iPhones, as well as a new Apple Watch and maybe other hardware too.