Looking at Nissan's online 2018 Leaf documentation, it looks like the portable dual voltage EVSE only comes standard with the SL Leaf trim. To get it with the S trim it appears necessary to get the Charge Package, and to get it with the SV trim it appears necessary to get the Technology Package. I saw no mention of any other portable EVSE (say Level 1 -- 120v only) from Nissan as an option for the 2018 Leaf.
Although it would be nice to have the portable EVSE standard on all Leafs, this would result in higher prices for basic S and SV Leafs -- EVSEs ain't free. The reality is that there are a lot of choices now for portable EVSEs for people that desire even more flexibility -- and many people (like myself) don't need a portable in the first place.
In any case, Nissan now for the first time is providing what looks like a very versatile EVSE: it can be used on a regular basis as your only EVSE to charge your Leaf at top Level 2 speed at most peoples homes (with proper 14-50 outlet installation) and on the road at many RV parks, or at Level 1 speed probably 80% or 90% of locations in a pinch.
A quick comment on proper 14-50 outlet installation for non-exceptional ones:
I believe the current NEC still allows this outlet to be wired for either 40 or 50 amps (usually means using 8-3 AWG for the former or 6-3 AWG cable for the latter). If you are installing new cable, the only somewhat more expensive (thicker) 6 AWG is probably the wisest/safest choice. I would also recommend using a 40a breaker if you use 8-3 AWG cable and using a 50a breaker if you use 6-3 AWG cable, as this way you can look at the DOCUMENTED(?!) EVSE breaker to more easily tell what amperage your outlet is capable of.
If I have seriously erred in the previous paragraph, please let me know so I can correct its text...
One last but important concept:
Keep in mind that the NEC rules concerning amps, wire thickness, etc are mostly there to try to properly protect a wire's or cable's INSULATION from damage due to heat, both short term and in the long run. You don't want excessive heat to cause the insulation to become hard and brittle (or even melting/burning!) and therefore unsafe due to possibly allowing arcing (fires) or short circuits or shock hazards.