SQL Server 2016 does not include SQL Server Manager Studio or SQL Server Data Tools (ie BIDS, Visual Studio Shell) as part of the installation. The SQL Server installation screen contains links to download these secondary applications. The default download link for SSDT will install SSDT/Visual Studio 2015. SSDT 2015 will not be able to read or migrate report RDL's created within the report designer that was part of SQL Server 2005 or 2008.
An additional complexity is that even if a user was on 2008 R2 or 2012 and the user simply used the "Add New From Existing" option to add a report that may have been created in 2005 or 2008, the RDL is NOT migrated to 2008 R2 or 2012. So moving from a 2008 R2 or 2012 to 2015 does not guarantee successful migration. I have narrowed down to two solutions that will successfully move a client's reports to SSDT 2012 or SSDT 2015 compatibility. Both solutions rely on a specific method to getting to 2012 compatibility.
1) The first option is to bypass the SQL Server link that takes you to SSDT 2015 download. You can instead install SQL 2012 (https://www.microsoft.com/en-us/download/details.aspx?id=36843), which is compatible with SQL Server 2016. You can continue using SSDT 2012 as your production report design unless you absolutely need any of the new design features that were added to SSDT 2015.
2) The second option would be to also download and install SSDT 2015, which will coexist with SSDT 2012. In this approach, you would first use option 1 to handle the migration to SSDT 2012. After which you can open the project in SSDT 2015, which will migrate an additional level. You can now edit and create report using SSDT 2015 features.
The key to either approach is the migration of your existing RDL's to the SSDT 2012 level. This HAS to be performed IN BULK and during the initial opening of the report project in SSDT 2012. You will also be given a warning that this is a "One-Way Process", meaning that after you click "Ok", you will no longer be able to open those RDL's in a prior versions.
A) Start your EXISTING non-SSDT 2012 reporting tool and create a NEW project (ie "Acclamare 2012"). Configure the project properties and create a Datasource. The reason for having two projects is that Step C below is going to alter the Acclamare 2012 project; and you will want to retain one project at your existing version.
B) Under reports, click "Add New From Existing" and select ALL of the report RDL's from your existing project. You in essence now have two projects with identical RDL's and versions.
C) Start SSDT 2012 and choose to Open a project. Select the project named "Acclamare 2012". You will be presented with a migration screen and the warning that migrating is a One-Way process. Click OK and proceed with next two screens. Once completed and reports appear in your Reports list, click on the top Project Name and choose Save from the menu. You now have a project containing reports migrated to 2012 compatibility level.
You can deploy and use these reports as is, or you can elect to install SSDT 2015 and repeat steps A-C. The only difference is that in Step A, you will be beginning with the newly migrated project "Acclamare 2012" and creating a "Acclamare 2015" project.
Important Note: If you have already installed SSDT 2012, you may not have used Steps A-C to populate that project's list of reports. You possibly created a project and used the "Add From Existing" option to add the reports from an existing project. That approach DOES NOT upgrade reports' compatibility level. These reports will be working fine in SSDT 2012, and that is because SSDT 2012 will still work with reports at 2005 and 2008 level. If you were to ever attempt to move forward to use SSDT 2015 or beyond, you will be stuck as the existing SSDT 2012 project is actually comprised of reports NOT at 2012 compatibility level.