In this blog the release schedule for SQL Server is explained and it becomes clear that SQL Server 2008 won't become available until 2008-Q3. Now aside from SQL Server 2008 not becoming available, this also means that the business intelligence suite which comes with SQL Server, the one you need to create SSIS packages and SQL Server reports, will not RTM until Q3. This in turn means that you won't be able to use these designers in Visual Studio 2008.

The Business Intelligence Suite uses the Visual Studio Shell and integrates in such an excellent manner that it is quite thightly bound to a specific version of Visual Studio. The SQL Server 2005 Suite is bound to VS2005 and the SQL Server 2008 Suite is bound to VS2008. So if you're planning on moving to VS2008 you'll have to run VS2005 as well, at least until 2008-Q3.