That's not a real issue.
You have multiple options to achieve this:
1) Join your data sources together, this is possible since Tableau 10 so you no longer need to worry about using multiple data sources
2) If you are working with an older version of Tableau, it's also possible to go for blending (http://onlinehelp.tableau.com/current/pro/desktop/en-us/help.htm#multiple_connections.html )
3) You can use dashboard actions to interact between data visualizations of different data sources (Actions )
4) You can create different visualizations and place them under each other on a dashboard to make it look like they are only 1 visualization
As you can see there are multiple ways to approach this
It is possible to build dashboard from multiple data sources. I have attached a sample using Sample Superstore and World indicator data source that comes ready made with Tableau Desktop.
Book1.twbx 1.3 MB