I don't know about whole albums but bands who I could see theoretically on a late 90s-early 2000s "classics" station:
weezer, foster the people, black keys, arctic monkeys, kanye, jay-z, the roots, outkast, justin timberlake, if i think of more i'll add them. i really can't see radiohead becoming more mainstream later on, they're a little too "unique." the only super popular song they did was creep and that was early 90s. i can't comment on the artistic quality or relation to their respective genres but as a regular joe with no knowledge of indie rock or whatever these are the artists that first come to mind. it's interesting though because what's popular in one moment may not last. i can remember growing up listening to a lot of alt rock and 90s pop rock such as everclear, third eye blind, live, counting crows, wallflowers, smash mouth, and a lot of that stuff didn't age, but weezer for example did.
a lot of mainstream and pop rap is shit tbqh, so i don't know how much that stuff will survive as part of a classics station. only ones i can think of are kanye, jay-z, and roots. certainly nothing like the heyday of hip hop in the early 90s with bands like beastie boys, public enemy, nwa, dre, snoop and pac, tribe called quest, etc. eminem may also survive but with those early goofy songs that are just really catchy. i don't count artists such as mos def, talib kweli, and so on because even though they're popular among college kids they just don't have one of THOSE songs that literally everyone knows. maybe talib, get by? roots may fall into the same category but i'll give them the benefit of the doubt given they have songs such as seed 2.0.