It is customary that before a big event like WWDC the online Apple Store will go down and during the keynote presentation the store will be updated, today is no different the Apple store is officially down. Today we are expecting mostly software previews of iOS 7 and iradio and maybe a few pieces of hardware will make their way into the presentation.
Rumours have suggested that they will announce Mac refreshes that will bump the specs and introduce Haswell as their new processing chip, other reports suggest that a new Mac pro will be announced today. Also the Airport and Time Capsule devices maybe updated so they are compatible with the new 802.11ac standard, if they do get updated it is most likely that they won’t be announced and will just appear on the Apple store updated. This maybe the case for the Mac Pro, the last fe updates to this product have not been announced at a conference.
The Apple store will be up shortly after the keynote is finished it normally takes an hour after the end of the keynote before it is fully functional again with the new additions to the site. You’ll be able to pre-order or check the products out after the keynote but until the store is up again you can watch the keynote again if you missed anything.