It's hard to say. It was expected Ukraine would launch a Spring offensive but now we're into early summer it could end up being another Autumn offensive. Perhaps they've had soggy weather to hinder preparations, but Zelensky's trip to Germany and to London where he again stressed the urgent need for aircraft suggest they're very nervous about making any advances without air support.
A prudent approach, as i see it. Pushing Russian forces back will take a great deal of effort and logistical support, so he has to be absolutely sure they have enough artillery, ammunition and armour to support the fresh troops who require training, especially in the new tanks.
The terrain is suited to defensive action and the Ukrainians cannot afford to lose more men than necessary. Russia has a plentiful supply of cannon fodder to throw into the breach and a High Command who aren't squeamish about losses.