The 3080/3090 reference card blocks are suppose to start shipping this week, and I'm guessing it's going to be first come first serve basis, as to when your order was placed to how much stock they have available to ship. The Strix 3080/3090 blocks are suppose to start shipping in the next 2-3 weeks. If you're wondering where I got my information, just check the German forum, and translate anything Stephan or Shoggy posts in regards to the cards.
So if you're placing your order for a reference block now, I'd give a ball park estimate of 2-4 weeks minimum before it ships to you, as basically you'd have to wait your turn.
Here's the link to the German thread in regards to the 3080/3090 blocks.
Kühlblock für die 3090 von NV? Preview Seite 11, Aktueller Stand Seite 18 / Preview Strix 21