Foss is part of the Sivakov, Bernal, Lambrecht generation, in which he was a distant dot. The only reason why he finally won Tour de l'Avenir, was because A/ he had the best domestique (who was actually much more impressive than him): Sleen. B/ he waited as long as he could, so he could compete with riders 2 to 3 years younger than him, while Pogacar, Bernal, Sivakov & Evenepoel all moved on from U23 and C/ he was lucky enough half the field of (younger) favorites crashed out or lost a lot of time. I would be very surprised if he turns out to be anything more than a domestique. Sosa can win a Vuelta, in the same way Hesjedahl could win a Giro. In his case, that means a tailored route without an ITT and nobody else competing. Gaudu: jury's still out on this one, I expected more from him by now. Also seems to have to peak for his top results, but considering he's been riding as a domestique mostly, hard to say. Leknessund is a great rider, but i'm not convinced he's going to be a GT/GC rider. I know he's been doing great at GC's in the youth ranks, but i could easily see him turn out to be more of a Cancellara type of guy. When i compare him in terms of power, with a guy like Van Wilder (who was nearly his equal last year as a first year U23), not only is Leknessund a year older, but he's also much more of a slim trained athlete who has less margin to lose weight without losing power, while a guy like Van Wilder can drop 4 kilo without it making a dent in his power output. Haven't seen enough of Rubio. Ardila seems like a top talent, if he doesn't wreck his own body. I hear he's already had knee problems, and the way he climbs he's bound to have more.
Personally, i'm also not convinced Higuita is going to be a top contender for GC. I can see him get a lot of top 10's and stage wins, but few podiums.
With some of the names listed, it's strange that Vlasov isn't, and also Almeida and Bagioli. Who says they will stay in Evenepoel's team until the end of times?
Imho, it's too early to say anything about the Brenners and the Uijtdebroeks, though especially these two seem like the real deal.