To clarify, Sakurai was going to meet with someone at a publisher to discuss some character ideas, but the building was closed down due to one of the workers getting coronavirus. Because of this, the development on this character is being delayed.
We have no idea if this character is F6, nor do we know if this will have any effect on the other characters or the scheduled reveals. All we know for sure is that one character is getting delayed. Yes, it's possible the rest of the DLC that was going to come out following this character will be delayed too, but Nintendo could just as easily ask Sakurai to move ahead to the next character and come back to this delayed character toward the end of the pass. Hard to say.