The preview release of the latest version of SQLServer, CTP 1.1 of SQL Server vNext, contains important new features and enhancements for Analysis Services Tabular:
Connection to new data sources as currently offered by PowerBI: multiple file types, databases, Azure sources and other online services, Big Data systems, Facebook, etc.
Possibility to perform data transformation directly on the tabular model: split columns, hide columns, change data types, etc... using a query editor in the style of Power Query and PowerBI.
Custom Drill down in Microsoft Excel: allows you to customise the data detail of a measure in an aggregated report. For example, when end users view total sales for a region and a month, they can see the associated order detail.
These improvements, together with the DAX improvements and security enhancements, will make tabular models the most recommended models in most scenarios. More details can be found in the following post from blog of Microsoft.