You don't know that. You dont know how late FighterZ is going to come to Switch, in fact it's already out elsewhere and for all we know, development hasn't even started on FighterZ Switch, IF and only IF it will even ever come since all that was ever said about it coming to Switch, a month or two ago was, quote from Tomoki Hiroki :
"In regards to the Switch version, we couldn't really say about the situation, however, what we do know is we would like our Switch users to focus on our first Switch title: Dragon Ball Xenoverse 2.
After the release of Xenoverse 2 on Switch, then we will start to consider whether we should have Dragon Ball FighterZ on Switch."
So according to him, development wouldn't even have started until AFTER Xeno 2 was released on Switch, IF it was to happen. The game is out now, and the Switch version if it exists may have only just started development. Porting a game to a less powerful platform and having it optimised enough that it is in any state you should wish to be able to play it as isn't something that can be achieved in six months. Could take a year, by which point for all we know there will be another super hot DBZ game already out on other systems.
Now having said all that, it sounds likely, now that Bannam has said they regretted not having developed more games for it sooner, that most of their hot games that have the potential to still run and look great on Switch will come to it, including FighterZ. But from what we DO know, development on it can't be too far along.