Improve Reporting Services (or converge it with Power BI). SSRS hasn't been improved very much in the last versions. For many uses cases SSRS still offers features such as export to several formats (...
Better integration between the tabular data source and SSRS for issuing and managing DAX queries. Not much use of hte tabular models are done with SSRS because the technilogies don;t integrate well. This is the same hurdle which was overcome in the early days of SSRS and integrating with SSAS before the tabular model was introduced.
