TV Line has an interesting spoiler for us. Not sure which episode it will be, but going by the title and timing, the spoiler could be for the episode 7.12 “Time After Time After Time”
Here the spoilers, thanks to Matt:
Supernatural | Should Sam and Dean get fitted for zoot suits? It appears that the CW series is booking a trip to the 1940s or thereabouts, seeing as a casting call has gone out for the role of – wait for it – Eliot Ness. Yes, as in the famous G-man who headed up The Untouchables. Specifically, the show wants an actor in his 40s who presents “an unyielding regality” and in a sharp suit is “the epitome of cool unflappability.” Oh, why am I still talking – y’all are busy imaging the Winchesters in zoot suits. Wakey-wakey!
Source: TV Line