That will be entirely up to Samsung. Since the S5, which was released over 3 years ago, is no longer supported by Samsung, I'd be surprised if they released anything for it. At this point the only devices they have as supported is the S8/8+. It was noted before on their official blog that Bixby will eventually be coming to other Samsung appliances (ie TVs, air conditioners) so that they can be controlled by the phone, but it wasn't clear if it would be expanded to previous generation Galaxy devices as well. Samsung just released Bixby worldwide to S8/8+ today (08/22).