At least not completely.
When you finally get your hands on the Galaxy S8 on April 21, word is that you won't be able to use Bixby Voice. You won't be able to dictate your messages or chat with the voice assistant as you might with Apple's Siri or Google Assistant. You'll have to wait. Samsung says that that the Bixby voice assistance will get rolled out in a software update "soon" but did not provide a specific timeline.
That's not to say that Bixby won't be there at all. After all, Samsung put a dedicated button on the side for it. Bixby Home, Bixby Reminders and Bixby Vision should all work, the last of which can be used to identify objects in the real world and suggest where you can buy them through online partners.
I got to fiddle around with a Galaxy S8 at the local Samsung store and when I pressed the Bixby button, it just booted me back to the homescreen. Hopefully that's not what happens in the final retail version!