I don't know about that; a new Pokemon character seems inevitable for any Smash game's base roster, but we didn't get any new Pokemon in Smash 4's DLC (seeing as Mewtwo was a veteran), or in Fighters Pass 1 (even though they easily could have added a Sword and Shield Pokemon, since it came out while FP1 was being released - it was late into FP1, but that didn't stop them from adding Byleth). It could happen, but it's not guaranteed.
Also, if you're referencing Avengers Endgame with the use of inevitable, it seems like an odd choice considering that Thanos dies almost immediately after both of the times that he says the phrase "I am inevitable", so it didn't really work out the way that he hoped.