It has been proven in the past that he had an incredible amount of potential. He surpassed Goku in raw power at age 11 in the Cell Games. It is more than likely that Gohan would be much, much more powerful than Goku if he kept training intensely during the 7 year gap that preceded the Buu saga.
That being said Gohan doesn’t train, and he was noticeably weaker than he was when he was a teen. Gohan received a considerable boost while training for the tournament of power, reawakening his mystic form. He was able to hold his own against Goku’s SSB form until he used the kaioken, and was taken down with one punch. Unless there is a need to train after the tournament of power, Gohan will begin to lose his power.
So when considering all this, it is more likely that Trunks will surpass Goku and Vegeta, provided that he continues to train. I say this because we have seen future trunks as a teen in action, but nothing of Goten. So any speculation of Goten’s power as an adult would be just that… speculation without any amount of sufficient evidence.