When you can play the album decades later and still connect with the songs, and recognize the talent and effort that went into crafting each and every song that is on the album, and you respect the artist for creating said body of work.. I think that's a classic album.
As examples, here are some albums from the 2010s I think have the most potential to be future classics:
Highest likelihood:
Adele - 21
Kanye West - My Beautiful Dark Twisted Fantasy
Kendrick Lamar - good kid, m.A.A.d City
Lana Del Rey - Born to Die
Taylor Swift - 1989
Semi-likelihood:
Bey's self-titled (the release tactic is going to down as classic, album itself is debatable)
Bruno Mars - Doo-Wops & Hooligans and/or Unorthodox Jukebox
Drake - Take Care
Katy Perry - Teenage Dream
They are all universally loved, defined a certain time in people's lives, and made a personal imprint on the people that listened to them, for whatever reason. They're iconic and were influential to albums/eras that followed.
If that album gives people that same feeling of enjoyment and appreciation even after years or even decades of it's release. I mean you cant really call a body of work a classic if it did not stand the test of time.