I've seen quite a few unconfirmed twitter reports to the effect that the offensive has started:
There has been speculation that the Russian forces on the west side of the Dnieper river are effectively trapped because the bridges are out and the Russian forces cannot be readily resupplied and they also cannot evacuate quickly. Presumably the goal is to crush the Russian forces.
Assuming this speculation is correct, the big question seems to be if the Ukrainian forces have sufficient manpower and firepower to execute the plan.
It appears to me that the Ukrainian forces may have feigned weakness near Kherson recently in order to draw Russian forces across the river into the trap. I have absolutely no inside knowledge whatsoever, so this is pure speculation on my part.