They really do need to explain this a little bit better somewhere, because we frequently have to explain that the date that you see on the web site is a target date for your units to ship out. It’s not set it stone, it’s an estimate based on a computer algorithm that calculates when your unit is likely to be ready to ship, based on a lot of variables going on at the factory and with the supply chain.
Having said that, if you are getting close to the date and it hasn’t shifted, Congratulations! You will probably be hearing from them soon! 
When your unit has been built and is ready to go, you should receive an email from Glowforge verifying your address information along with instructions first…(I think…keep in mind we didn’t do it this way.) Then your unit will ship and you will receive it depending on how far away you are from the factory in California where they make them, what the weather conditions look like across the country, and whatnot. New units ship via UPS ground…you will definitely want to sign up for UPS MyChoice if you want to track the actual arrival. (Sometimes Glowforge gets the arrival notice out to you after it has already arrived, which is kind of amusing. Given the excitement of arrival, no one really cares by that point.) 
Anyway, now is a really good time to prep your area for it’s arrival. Get the table ready. Get your vent port set up if you are doing one so that you can set it up and go.
Also a good time to read through the “Getting Started” training here so you can hit the ground running.