This news comes via frontman Win Butler, who appeared on the most recent episode of the basketball podcast The Ringer NBA Show. Fan account @ArcadeFireTube transcribed this back-and-forth:
A new Arcade Fire single coming out this year.— Arcade Fire Tube (@ArcadeFireTube) February 15, 2019
Q: You said you were recording...
WB: "Yeah, just working on a track. It will actually be out sooner than later".
Q: Really, possible Arcade Fire single coming out this year?
[Win Butler on The Ringer NBA Show podcast]
@ArcadeFireTube also pointed out that multi-instrumentalist Richard Reed Parry was recording earlier this month in New Orleans (where Butler and Régine Chassagne live):
Richard was down in New Orleans on Feb 2nd recording with long-time Arcade Fire producer Markus Dravs. Feels like it could very well be connected to this. [Instagram: rrparry] pic.twitter.com/OVQ4ZHDNAo— Arcade Fire Tube (@ArcadeFireTube) February 15, 2019
Arcade Fire's most recent album was 2017's Everything Now. More recently, they collaborated with New Orleans musicians to create a theme song for the city's Krewe du Kanaval.
Listen to Butler's episode of The Ringer NBA Show here.