I thought Adidas were only doing one team per league but with a mega deal, i.e. Real Madrid, Bayern, Man Utd. Nike apparently taking a similar stance with Barca, PSG, Chelsea (next season). New Balance threw big cash at Liverpool and Puma did with Arsenal. Wouldn't be surprised if it was Under Armour or Reebok given all the other bigger clubs have different sponsors.
Doubt it would be Reebok, as it's basically just Adidas in disguise. Reebok is owned by Adidas Group.