What do you mean by GANs-as-a-service here? I'm not sure that our understanding of GANs is refined enough to offer something like "a framework for letting non-experts train a GAN to do cool things" outside of a very limited scope - there are lots of issues with things like making sure that the generator/discriminator converge and avoiding oscillations back and forth between either winning, that can unexpectedly ruin your training.
On the other hand, if you mean "startups that use GANs to build cool systems, such as manipulable latent spaces for interesting data" then I totally agree! For example, we're using GANs to train voice conversion systems, which let you manipulate a space of voice representations to make new voices, which you can then sound like. I definitely expect to see a lot of startups doing interesting things like that popping up!