First: I am by no means an expert on MagicJack. However, I haven't found documentation about a 2018 vs a 2017 model. My impression is that the MagicJack Go, which is the one I bought from Best Buy, is the most current model. The "Go" comes with 12 months of service included.
There is an "Express" model which comes with only 3 months of service included. People say that it is a less expensive way to try out the service. Other than some cosmetic differences and the different lengths of included service, my impression is that these two are the same.
Note that the "Go" is black with blue trim, while the "Express" is white with blue trim. The "Go" is the only product listed on the MagicJack web site.
Someone else might have better information, but I just don't find any info about a 2017 vs 2018 model of the MagicJack Go.
This does just what I needed, by the way: providing a landline for use during long conference calls.