They did the same Mythical distribution in 2016 and SM released in 2016. Also, interestingly, there's no distribution for December. Furthermore, this is just speculation, but there's rumored to be a Pokémon announcement (and Animal Crossing) in March, and generally, a new gen gets revealed 9 months before the release date (XY were revealed in Jan, released in October, and SM were revealed in February, and released in November), so it's possible that if the analyst's prediction is true, we might have a reveal in March, and a release in December.
Beyond that, another interesting thing to note is that Nintendo of Europe sent out surveys asking people which games they would be most interested in buying in the next 12 months, and Pokémon RPG on the Switch was one of the options.
I'd say, there definitely are many hints that seem to be hinting a late 2018 release. However, I feel that if we don't get any news by March, then a 2018 release should be ruled out, and maybe we'd see gen VIII in early 2019. But whatever the case, I just don't see gen VIII releasing in late 2019. With the UB arc already starting in the anime, with both Necrozma forms revealed, the anime definitely can't last longer than Feb/March 2019 tops. Furthermore, they don't have any more gen VII Pokémon for a 2019 movie anyway, since Zeraora is the last gen VII Pokémon, and is most likely going to appear in M21.