Team Rocket don't always rely on their Pokémon to get what they want. They may use a new Mecha to create problems for Ash and his friends. In AG they seriously interrupted Ash's gym battle against Liza and Tate by destroying the gym's roof and making off with Solrock and Lunatone in a giant Robot - We might see something similar happen here.
Even in the event that they use a mecha to interrupt the Gym match, I hope Olympia gets rid of them herself with her psychic powers as a way of bolstering her own hype. Ash can have a seat.