One of the biggest mysteries in Dragon Ball Super's "Universe Survival" arc and the Tournament of Power has been the debut of Goku's new "Ultra Instinct" power. It first manifested during Goku's crazy battle with Jiren (ep. 109 - 110), and then again showed up when Goku was battling the fused might of Kefla (ep. 116); however, the exact nature of Ultra Instinct is a big looming question, as is its evolution.
Vegeta will be trying to master Ultra Instinct as the Tournament of Power goes on, but as one line of fan theory speculates, the Saiyan Prince may be taking a different route to get there! Teasers for Dragon Ball Super 117 tell us that Vegeta will be trying to use Ultra Instinct in the upcoming battle with Universe 2, but won't quite be able to manifest it the same way Goku does, and will end up paying the price. However it's the details in Goku's use of Ultra Instinct that may make the difference:
In episode 116, during Goku's battle with Kefla, Tien and Whis have an exchange in which they discuss Kefla's power and how she's able to stand against Goku's Ultra Instinct. Whis claims that Goku's attacks aren't that effective - which fans have instantly seized on as a major development and clue about Ultra Instinct's use - and where it could come into play for Vegeta.
Defense + Offense
It seems to be made clear in episode 116 that, at present, Goku has only half-mastered Ultra Instinct, using it as a defensive measure. In other words, when dodging or countering attacks, Goku is reacting without thinking at such speed that taps into Ultra Instinct - but when trying to launch offense attacks, Goku still requires too much thought and analysis to fully utilize Ultra Instinct's potential.
That's where Vegeta comes in:
Dragon Ball has always played up the yin/yang aspect of Goku and Vegeta's rivalry, with the latter always serving as the more aggressive and cocky fighter. The nature of Vegeta's personality and entire philosophy to fighting have fans speculating that his form of Ultra Instinct will therefore be based on offense attack, rather than defensive technique like Goku's. Vegeta has only seen Goku's method of achieving Ultra Instinct, which will probably lead to the misconception that gets him hurt in episode 117. The Saiyan Prince has always been a quick study though, and when at first he doesn't succeed, he'll likely discover his own path to Ultra Instinct through the crucible of hard combat.
This wouldn't be a shocking new development for Dragon Ball - Vegeta has a long history of achieving new power or transformation by first seeing Goku do it, and then finding his own pathway to the same destination. More importantly, this fan theory leaves the door open to a possibly big finish in the Tournament of Power: Goku and Vegeta fusing into Vegito, thereby creating a more powerful fighter who has mastered both halves of Ultra Instinct. In the end, it could be the only hope of defeating the massive power of Jiren!
Dragon Ball Super airs on Crunchyroll and Funimation NOW Saturdays at 7:15 p.m. CST. The English dub airs on Adult Swim's Toonami block Saturdays at 11:30 p.m.