While I agree with
@ryanosaur that you should check with the Roger Russel page, and I agree with
@TLS Guy that in-wall runs do end up being a bit longer than some expect, I will disagree completely that things are going towards 'Ethernet' wiring for audio. Active speakers have been around for decades, and audio over network has been around well over a decade now, and it is barely starting to take hold in the commercial realm, at really high prices to implement.
The traditional amplifier and amplified speakers with speaker wire will be around for decades and decades more. There is some movement towards networked speakers, but that movement is tiny. It also isn't going to go away. Not with the cost associated with unpowered in-wall/ceiling speakers. It just isn't. So, you absolutely do not need to put speaker wires into conduit and go through the expense, or hassle of conduit for speaker locations. I would argue that it is pretty ridiculous to think that 60+ years of traditional speaker wiring is about to be completely changed anytime soon.
I would say, if someone wants to be absolutely sure, they could run a cat-5e/6 cable alongside the speaker wire. This is way less money than conduit... by a mile. It also would likely never be used. Ever.
So, don't worry about the conduit. Do consider 12 gauge cable, or maybe 14/4 cable (this is what I often use) and call it done. Keep it simple.