I've got something to say here. Gon and Killua have already past Netero potential wise by the Hunter Exam. It becomes very apparent that Hisoka and Netero both seek out opponents whom they'd like to spare against. Netero first notices the boys on the airship.
Here we get out first taste of how truly exceptional Gon and Killua are. First from Netero acknowledging Killuas talents for the assassination arts. Then eventually his keenness on Neteros use of only one arm and leg.
Gon is shown to be faster and more agile than Netero even believed. However Gon ruins this opportunity by jumping too high. Eventually though even after Killua had left, Gon gets even closer to taking the ball from Netero. He even charges Netero with a headbutt strong enough to lay him out.
Now my actual proof that Gon and Killua had surpassed the chairman comes from the ant arc.
Think back to when the chairman asked Colt for his opinion on his Nen. Colt said he would be killed by one of the royal guards. Flash forward to Netero encountering Pitou and we're given the Zeno explanation of "Spirit Echos". Obviously this happens here because it explains Pitou and Netero are close enough in strength to have heard one another's thoughts in that interaction that lasted a tenth of a second.
Now go to where Gon is with Pitou walking into the forest. At no point can Pitou hear what's going through Gons head. She can't even survive a basic kick well enough to reposition in the air as she had against Neteros swat. Fast forward a little bit and Killua arrives. He sees Gon lose his arm to a Nen controlled Pitou corpse and then hears Gons "Spirit Echo" about how it's okay now. Clearly Gon and Killua are similar in strength, but apparently Pitou wasn't?
Why would there be such an emphasis on how powerful Netero is, but he cannot seriously injure the two ants we see him try against? Zeno warns us of his ability and then we see it do nothing physically. Gon basically kills Pitou with a kick.
Netero was 45+ when he began training on the mountain and could maintain ten for (I think like 18 hours?) before collapsing. Gon and Killua at 12 or 13 could maintain their ten for 3 hours during the one month of training during the Knuckle training. Bisky says something like it takes a month to prolong your ten by 10 minutes. Killua goes from 55min to 3hours in a month.
That means Killua could theoretically reach Neteros nen/ten control in 7 months. Now obviously Gon and Killua arrive at their destination early because their the main characters, but it should not be understated that Biscuit said all of the ten related stuff and as a 2 star hunter who knows the chairman, she's probably pretty accurate about all of it.
From here we just need to think about whether Gon and Killua are genetically stronger than Netero. If the two are capable of even saving a year or two in ten training then they all ready be better than him before age 50 at nen control. From there's it's just determining if Ging or Silva are stronger than Netero. We never see Neteros lineage, but he obviously comes from someone capable as he dies at 100+ year of age.
Personally I don't believe Silva is that strong since he states that killing a Troupe member wasn't easy and Zeno even says to kill both him and Chrollo and he literally can't. That's for another day. Today I'm saying that Gon and Killua could, would, and should surpass Netero