It's an interesting remark. Over the last 5 years the Tour win has been absolutey unreachable for mortals (i.e. non-Pogacac, non-Vingegaard guys) and it seems the streak will continue as we need two guys to be down like in 2014 (even if something happens to Pogacar Vingegaard should still win the race comfortably).
Seixas is most likely simply because his prime won't overlap with those of Pogacar and Vingegaard but there's no guarantee he will ever reach the level required.
Well to be honest I think Vingegaards level might not be unreachable for Del Toro if his progression continues a bit further than where he is at now. Pogacar has also improved quite a bit after his first Tour win, and I think it is quite likely that Del Toro will at least build out his durability over the next seasons if nothing else. I would say there is a decent chance Del Toro reaches Vingegaards level next season or the season after.
For Seixas it is even more reasonable to think that he can match Vingegaard current level at some point in his career. Perhaps it will take him one or two seasons longer than Del Toro because normally his prime should be a bit further away. But then again Seixas already seems quite complete.
It can also be argued that Vingegaard might detoriorate a bit from 2028 onwards as the prime years for GC-riders seem to be a bit younger than they used to be. So I think it is likely that from 2028 onwards Vingegaard is beatable for some of the better up and coming contenders.
Pogacar is a different beast though. He is much better than Vingegaard and also younger. If he doesn't get a big injury or misses out on a Tour I think he will win the next 3-4 tours for sure. Guys like Del Toro and Seixas should probably hope he gets tired of cycling after that.
