As an art dealer, I am often asked what artists are people collecting. This is a hard question to ask because there are so may types and price points of art available.
I see younger people interested in Street Art/Graffiti Art. They like Mr. Brainwash, Banksy, and Basquiat plus many many more! They are also still interested in the Pop Art masters like Andy Warhol and Keith Haring. Their work is still speaking to people long after their deaths. Given the greater availability of Street Art, I can only guess what the long term values will do. Like most art, I'm sure the best works by the best artists will continue to be collectible.
Mr. Brainwash, Mick Jagger Jean-Michel Basquiat, Charles the First