I found this cool explanation [here](https://www.kanzenshuu.com/translations/saikyo-jump-june-2014-issue-twel-buu-mysteries/) in a Q&A session. Someone asked Toriyama this:

>Goku endlessly keeps getting stronger, with Super Saiyan 3 in the manga and Super Saiyan 4 in the anime; does Super Saiyan keep getting limitlessly stronger too? Might we eventually see things such as a Super Saiyan 5…?!

And he responded with this:

>Super Saiyan 2 and 3 are nothing more than powered-up variations of Super Saiyan. After the fight with Beerus, Goku realized that mastering his normal state and Super Saiyan would raise his level more and sap less strength, so I think he probably won’t become Super Saiyan 2 or 3 any more.

It would be great if Cabba and Caulifla eventually focused on dropping any regular form above SS1, and focused pushing it as much as possible. Like, even beyond what Goku ended up doing. So then we have Cabba and Caulifla only using SS1 as their regular-ki form, which ends up being as powerful or even more so than they would've been had they used SS3 instead.

We've seen Jiren's main advantage be ki-control, which is what really made him so crazily powerful (as well as just being powerful in general, but his ki-control was the big deal). It would be awesome if this becomes the case with Cabba and Caulifla as well.

If they go into God ki territory, then it would be awesome if they stayed in SSG for a long time and made it crazily strong, and only later move on to SSB. It would help make them stand out, since Goku and Vegeta still mostly use SSB as their forms (with occasional UI and UE). 

Resurrection F already brought SSB early in and overshadowed the Red form. It would be great if SSG becomes the iconic form of U6 instead (since we missed that opportunity for U7 after RoF).

As for Kale, well, she can just push on with her controlled status. Get as much out of Full Power Super Saiyan as possible. So basically, if we ever do see the U6 Saiyans again, they should be very powerful but without a whole lot of different forms. UI and UE or whatever else can come way later. 

If we ever see the Universe 6 Saiyans again, they should use Toriyama's quote on Super Saiyan power