I watch a lot of zekken's streams and I think I know since when SEN has been working on the new Icebox. Zekken did stream on April 3rd and played only omen, about 4 games on stream (https://tracker.gg/valorant/match/d3622c11-039d-475e-ab78-dd6df84d6aac). After they lost to KRU, it looks like they have been working on Icebox with Omen for a months now, I now zekken bottomfragged that map today but his util was pretty good (need to work on some paranoia lines), especially his smokes were confusing G2 a lot.
Discord