When are project disruption skins going on sale?

Um. Not any time soon. They literally just came out.

With the implementation of the "early sale," which was close to the end of 2015, Riot no longer puts skins on sale at launch. All newly released skins will now be put on sale within 4-6 months of their release guaranteed. Also, this only applies to non-Legacy skins.

http://na.leagueoflegends.com/en/news/store/sales/were-changing-discounts

All non-Legacy skins will go in the sale 4-6 months after release. ... Bringing all of our skins onto the same early sale schedule means there will no longer be a launch sale for 1350s and Ultimates starting in the new year.