There have been no signs as to what will happen in Russian Doll season 3, but as fans of the show, we can speculate on how the final chapter of the trilogy will unfold.
Most significantly, we hope it will eventually reveal the identity of Horse. The horse is the weird homeless man Nadia has encountered countless times in the past while traveling through time. The season 2 finale implied that he might even be involved in making things happen, although we don't know what his actual involvement is for the time being (check out more of our Horse theories).