FRAND and 5G
This isn't as easy as you think. When ITU starts working on a 5G standard (maybe they already are?) they get a bunch of companies together who want to participate. This will cover everybody who is anybody in the mobile world, from the chipmakers like Qualcomm to phone makers to carriers. In order to participate, they have to agree to license any patents they have that get used in the standard under FRAND terms.
They can't hold back a few patents and think they'll use them to screw people later, they can't participate in the standards and try to steer them in the direction of their patents and then pull out before signing them over (Rambus tried this, look what happened to them)
So the only way you can hold a patent that is covered by 5G that you don't have to license on FRAND terms is sheer luck. Without any ability to see what direction 5G is going or being able to steer it in the direction of patents you hold, you have to just hope that you have a patent that will be covered by it, and that none of the dozens of corporations with vastly greater expertise in the mobile world are able to invalidate your patent with their own prior art.
Not saying it can't happen, but the ones who hold 99%+ of the relevant patents will already be at the table because they want to be. They aren't trying to get rich on the patent revenue, they are trying to get rich by knowing what direction the standard is going ahead of time and perhaps being able to steer it in the direction of something they already have expertise in (i.e., if they hold patents that are relevant, they already know what they're doing that area)