I'm not sure what you are asking for here? Are you looking to view the connection properties for a given SSIS package in XML format, or are you looking to have an external XML file for each connection that you can change when moving to different environments?
If you are just lookingto view them, you can view the .dtsx file in any XML reader including Internet Explorer. If you are looking to store these connections (or portions of them such as server names) externally in XML configuration files, you need to do this in the package configurations section of each package you are working with. Search "Package configurations" in books on line for details on how to do this.