Does Visual Studio 2010 Professional have the Diagramming support announced on the web? Do I need to install the TS version to be able to get these features ?
It's too early to get a definite answer: the phase when a product group defines the exact packaging and licensing is just beginning.
Heard it is available in VS2010. But not sure about edition specific features. It is yet to declare.
Check this: What’s new in Visual Studio 2010 Rosario
The Modeling tools can be found in the TS Version of Visual Studio 2010 Beta 1.
They're there -- the UML diagrams, if that's what you mean (at least in my version -- VisualStudio Team System 2010 Version 10.0.20506.1.Beta1).
Select File -> New -> Modeling Project.
Then in the Solution Explorer (the window on the right), right click on your Modeling Project (whatever name you supplied -- default is ModelingProject1). Then select Add -> New Item -> Sequence Diagram. (Or Activity, Class, Component, Layering, Use Case).
According to the Microsoft website, only the Ultimate Edition of Visual Studio 2010 (full relaease not Beta) comes with the UML Modelling Tools:
http://www.microsoft.com/visualstudio/en-us/products (Under 'Architecture and Modeling' features)