I think arcade will become more active than parkour, but maybe replace an other gamemode instead, because parkour is a solo game which you can play alone like mentioned before, and I think Tower defend isn't played that much too.
Yes let's do it! Let's go!
Ok in all seriousness. Let's not do this. If Cube implements Arcade again as a whole that would mean that all the Arcade games would split-up again just as the player base. And that would mean that you won't get enough players to get your Arcade game even started. I know what I'm talking about. I've been there when Arcade was almost dead in summer 2018. I would love to get Arcade back as a whole, but looking at the player base on Java right now I don't recommend it.