Yes, definitely can be used heavily for the both, porn and gambling. It ads a layer of anonymity to the both of these user's which can become very handy. Look at the recent hack of Ashley Madison for example. I bet their users wish they could have paid in bitcoins.
The key thing that I don't know is how will the regulators react to this idea, connecting Bitcoin with both of these industries. Under 18 problem can be a huge obstacle in my opinion and how to prevent minors from using these services.