Here is a "official" sounding quote saying that Nissan will issue the software update on Leafs built within specific dates:
"A Nissan spokesman told electrive
that they would offer the for all Leaf models produced between 8 December 2017 and 9 May 2018. Electric vehicles with a later production date already have the current software version."
Please post if you are able to get any further information from a dealer or if Nissan contacts you.
On a related note, how do I find out what year and month my 2018 Leaf SV was built? I tried the VIN decoding tools but I cannot find sufficient or clear info on how to figure that out...