Tough question! There are a number of things that come with being an expert/senior in any field which most certainly applies here too. There are two main roads to follow: (1) manager role (2) specializing and getting more responsibility.
The manager role is straight forward. You get promoted to lead your User Experience expert group, if the company is big enough or your company invests in the field of User Experience. Now, that’s not always the best thing assigning the best specialist to take on a manager role, since a manager (in my mind) should be a leader and not an expert. You waste your competence managing other people where you could make a difference with your skills.
It would be better to choose the other road - increasing skills either in general or specialize in a certain field such as Information Architecture, Interaction Design or Usability Testing or even narrower such as Card Sorting expert or Ontology specialist?
Its very hard to say when one will get promoted/more specialized since there are a lot of unpredictable variables such as:
- "Is there a position open?"
- "Is there going to be a reorganization sometime soon?"
- "Does the company grow and needs to hire more employees?"
- "What will happen in world economy, and will Greece stay inside the Euro zone?"
That's why "when" cannot be answered correct.