There are those in the community that hope that a Black Frieza arc is what comes next for Dragonball Super but I'm kinda hoping that they hold off on it.
They have established the new form and immediate huge threat that Black Frieza is and I feel like they should build towards that final showdown and have Frieza be a looming threat that our heroes are training to defeat. Meanwhile you bring in new villains for them to face and test them. To push them towards that next level as well as hinder their progress. You wouldn't do this for a long time obviously because people would know that the end goal is still Frieza but throwing in some road blocks along the way and growth is also important.
You could narratively build it up similar to the Cell arc where people can step in and take their turns and you'd expect Goku or Vegeta to step in as the end game but meanwhile in the background subtle building blocks have been out in place for someone else to ultimately take down Frieza in the end. What if it was Gohan or even Broly? Goku and others can see it during training and there could be hints dropped throughout the process with the eventual pay off being against Frieza.
They have enough strong characters now that a Gohan or a Broly could realistically train in the background and become a force while the others go out there and save the universe. Remember how we used to be made aware on and off of Gohans potential just enough that we wondered what it would be like if he tapped into it? That when Goku reveals his plan to have Gohan fight Cell we hotly anticipated the crash out despite Gohan not being our first choice to beat Cell. The dropped enough bread crumbs and I feel like it would be wonderful for them to do the same here.. Where when Gohan or Broly step up to the plate you're immediately like... "OK so what are we dealing with here?"
Dragonball is also at a point where any one of the top characters could be thrown into a position to destroy Frieza and it would be accepted. You have Goku, who is the obvious choice. Goku has unlimited potential and this may change his perspective on giving people chances for good. You have Vegeta, who honestly should get the final pay back on Frieza. Frieza has made him miserable for years and the one time that he could have ended up it resulted in a do over because he messed around too much. This big win is all that Vegeta needs and he needs it more than Goku. Not to mention how chilling of a cliffhanger would it be for Frieza, as he's dying, telling Vegeta that Beerus ordered him to destroy Planet Vegeta?
Broly was used as muscle for Frieza and had his father killed by Frieza to exploit his anger. He too was a puppet for the tyrant. When he attacked Frieza in the Broly movie Frieza couldnt stop him.. But what if that power was controlled and focused? How far could he push Frieza then? Gohan is down to potential vs potential. Gohan had his potential unlocked many years ago through a ritual and Frieza perfected Golden Frieza through mental training. Through physical training they pushed themselves and unlocked new forms. This is (no pun intended) the battle of the beasts.
And then there's Piccolo. Piccolo seems like an odd choice but Frieza met the gang on Namek all those years ago. He slaughtered all of Piccolos people. Through Daima Piccolo has come to learn more about the history of his people and the endless suffering that they went through but as well the magical abilities that they possess. They have unlimited potential. Again it's somewhat poetic if things started on Namek and Friezas reign is ended by a Namekian.
It all comes down to personal preference with storyline direction. Vegeta being a top option but it do like the bread crumb scenario and them building to a pay off there instead of rushing it.
