I say wait for 2-3 weeks of combat and Russia will be weakened enough to allow swift Ukrainian blow all across the eastern front.
For Ukraine now it's imperative to kill and destroy as many Russian unit as possible while keeping their forces intact. Trading space for time, until all the promised weaponry are delivered.
We might not even see any advance towards Kherson for a while, Ukraine might opt to wait in ambush of any Russian advance towards Mykolaiv or limited raid into Russian controlled territories.
My best guess is mid May to mid June. That's the timeframe where Ukraine will be strong enough to punch back against a severely depleted Russian army.
Ukraine has by the time of this writing had achieve tank parity with Russia due to Russia extreme losses and Ukraine kept capturing their tanks. The inflow of more than 250 MBT's from Poland and Czechia as well as artillery and other equipment will allow Ukraine to outmatch Russian early numerical superiority.
NATO might also (if not already) plays a helping hand with intelligence and planning in the upcoming Ukraine's offensive, as
@tracer had previously note with Sigint and battlefield surveillance cooperation.
The Russian invasion give the West, a once in a time opportunity to de-militarize Russia without having to sweat and spill their own blood. For the US this means neutralizing Russia as a long term high end near peer threat for a very long time on the cheap so that they could use their resources for the China fight in the Pacific. And for Europe this means return to a rational defense policy , after this debacle Europe economic policy will no longer trump military spending. The peace dividend of the end of Cold war is officially over.
Putin after all is not the master strategist that we all used to assume.
