There is some logic to the MY'18/19 designation.
Remeber that the 2013 LEAF which was the first US-produced EV by Nissan did not hit dealerships until February/March 2013 and the 2014 car followed shortly after that in August of 2013.
2018 could be a short year as well for the LEAF with the 2019 car and its variants arriving in dealers lots in November/December of 2018.
But regardless if it has a 2018 or 2019 designation, the new LEAF is an excellent car, I've driven it, have spent time with Nissan to understand their design goals, and I recommend the car. I also have an SL in Pearl White/Black with the light-gray interior on order.
What's cool about the LEAF is that it is what it is, and makes no pretenses to your vanity or otherwise. It's a contemporary-looking, value-priced, well equipped, very reliable EV for everyone. The LEAF is for those that may have modest to midrange means but wants to drive a new EV and for those that have the means but are smart with their money. This tactic is why Nissan owns this under $35(6-7)K space.
Nissan will be building a version of the LEAF for everyone over the next couple of years. I think that this current version is going to be around at least until 2021, and later be joined other types of EVs from Nissan that will continue to push the cool and practical EV space.