Highly unlikely that Ukraine will capture anything for the rest of the war.
What they can do is to manage to hit Zaporizhhia nuclear plant and cause deadly radiation not just in Ukraine but for the whole Europe.
IMO, WW3 will start when NATO actively engages in Ukraine. So far they have thousands of "volunteers and contractors" and supply weapons and ammo but it's still unofficial engagement. Large portion of Ukrainian army today already consists of NATO soldiers. What could happen on July 11th is decision to declare the war officially.