In those 5.5 years, did you ever work with SSIS, SSAS or SSRS?

BI developers will be in demand in the future, but their skill set will probably go beyond those 3 tools I just mentioned.

Big data is becoming more and more important (or maybe the hype will die, who knows), data visualization is getting hot, cloud is also worth mentioning and so on.

The biggest advantage you have as a database developer is that you know how to write SQL queries. If I were you, I would start out as an ETL developer (the biggest part of a BI project) and slowly work towards the other tools.