In the future the Levim will become Kohanim:[1]
The Arizal states that in the future, the Levim will become Kohanim. This is because the Levim contain a higher revealed level than the Kohanim, just as Gevurah contains more strength than Chesed. In the future, the Jewish people will be on a level that they can receive from the Gevuros and hence the Levim will become the Kohanim, the ones who channel G-dliness to the Jewish people. The mistake of Korach was that he desired to become like the Kohanim even now, before the redemption, when the Jewish people are not yet ready for such revelation.
[1] Likkutei Torah 54a