In the recent dragon ball super preview for episode 122 it depicts vegeta and goku pushing jiren back in the super saiyan blue forms. But how could this be possible if a Universe 7 Super Saiyan Blue kaioken times 20 couldn't even do this? Well I believe the reason for this is that vegeta has unlocked Super saiyan Blue 2.
as you can see from the image vegetas hair is more defined, sharper and he's more muscular similar to how it was as a super saiyan 2.
Super saiyan blue 2 can be one of the only things that can justify vegeta being able to keep up with jiren but we'll never truly know until the next episode of Dragon Ball Super!