The first part to do with marriage I'd highly doubt we'd ever see (at least an official marriage), because there are laws being put in place now to stop us from making AI "too smart" and I'd imagine if we get to the point that they can consent to stuff like marriage (and they truly consent in that they could have chosen not to and they understand the gravity of it and it isn't just a random decision), it is probably already past the point that the laws are trying to stop them from developing to, as the abilities involved in that will transfer over to things other than marriage. I'm not sure where the line is, so we might eventually see that, but I think the line will be drawn before that and the law will stop them reaching that point. It might happen without the robot's consent, or with "consent" that isn't real informed consent (so wouldn't be legal if it was a person who didn't have the ability to be fully informed as they'd be classed as unable to consent), but that seems unlikely too. I guess we'll see whether it happens in our lifetime or not. Plus more than consent comes in or gay marriage etc would have happened sooner than it did (which was ridiculous, that should have happened earlier, but it shows that it is about more than just consent). I doubt we will see marriage with robots outside of fiction.

As for the sex stuff, that wouldn't overly surprise me. There's porn of just about everything, so if humanoid robots became freely available and affordable, I have no doubt some people would have sex with them. I don't think it will reach the point that everyone chooses robots over people or anything like that, simply because not everyone will, but some people would do sexual things with them, regardless of if they are made for that or not. Whether it reaches the point the market starts making sex bots specifically is another question, but if the demand is there that wouldn't surprise me either. Robots made for that purpose wouldn't need the same level of intelligence as ones able to consent to marriage etc too, so that also makes it more likely than being able to legally marry a robot. If they did have that level of intelligence, that would actually make the whole thing more questionable morally since they should probably be able to choose to consent to sex or not then too, so the level of intelligence needed for consenting for marriage would likely be a con in this case.

It will be very interesting to see how AI and robotics develops over time but we do have a legal ceiling on how smart they can be and already it's getting interesting, both in terms of the really intelligent ones (i.e. ones the average person can't get hold of) and in terms of what is available to individuals too. There's a big difference between those two groups, but both are advancing and it's interesting to see. I don't know what the far future holds in terms of robotics and AI, but the near future looks like it could be very interesting.