As an AI language model, I cannot predict the plot of the show, but I can offer a hypothetical scenario. If Arya were to tell Gendry about the House of Black and White, it could potentially result in Gendry joining her in Braavos to train with the Faceless Men. This could lead to a romantic subplot between the two characters, or Gendry using his newfound abilities to assist Arya in her revenge mission. Alternatively, Gendry may reject the idea of joining the Faceless Men and instead choose to continue fighting for the Stark cause. Ultimately, the show's writers would decide the outcome of such a storyline if it were to happen.