Trying to cancel out during the streaming server connection (a sometimes-fix for this issue) is now giving “Unable to download game data from Blizzard’s servers. Please check your internet connection and try again later.”
This is a NEW error with the patch which just went live 15 minutes ago, compounding the existing issue we are experiencing when connecting to streaming servers.
Edit: Not getting the message anymore. Now, cancelling just pops up bnet launcher again. I switched regions to Asia, updated for that region, switched back to Americas and had another update (in addition to the original update).
Edit 2: Finally switched to preparing game data. Been at 0/54k for 5 minutes. 
Edit 3: Woo! In! 