They released it https://www.strymon.net/product/bigsky-plugin/
It is a bit expensive though (200$ excluding VAT, 239€ at Thomann !)
I have always wanted to get a big sky, but comparing the actual plugin to the reverbs in the Kemper, i think the only interesting reverb you can't really match with our units is the Cloud Reverb. Other feels a bit cheesy (i think i prefer the Hall in the Kemper to the big sky's Hall), average, or considerably inferiors (spring reverb).
I guess CKemper considers the reverbs in the Kemper to be final but i would like to have a good aproximation to the cloud reverb which seems unmatched to me.