That's a bold call from the US bank, as they say that:
"We expect the SNB to hike its policy rate by 25 bps to -0.50% on 16 June and exit negative territory by the end of 2022."
I don't think many market watchers are quite prepared for that and it is also evident in the action in the Swiss franc. The SNB and BOJ are the two old generals left in the evolving battlefield. But the times are changing and if the SNB decides to take its leave, there's going to be hell to pay in markets.