>>50196436>>50197760Evolving Skies has some of the most consistently popular and expensive pokemon across the entire series featured in the set:
>Rayquaza>Umbreon>Many other eeveelutions>Many other less popular but charasmatic pokemon in cool posesAll of these got alt arts. And Rayquaza and the Eeveelutions also got TWO (2) alt arts, one V and one Vmax version. If you were to shortlist 5 pokemon that consistently draw attention and money, eeveelutions and Rayquaza make that list instantly -- and especially if that eeveelution is Umbreon (although even leafeon and glaceon have their fair share of fans). Hell, Charizard in brilliant stars only got one alternate art.
Of modern sets, Evolving Skies is pretty safe. People are going to want to open that forever. It's one of the times where you can actually see the future for a product and it's value, it's just that good of a set. The sets that surround it, however, are full of more speculation but will likely rise as well (fusion strike being a sleeper-hit, btw).