What are the risks if Client does upgrade from Teleview to TPX?
CA Teleview has been 'stabilized'. It means there will be no attempt to fix any defects if a client comes up with a request.
On the other hand CA TPX is still supported and is expected to replace all instances of CA Teleview in the foreseeable future.
The risk of staying with Teleview is obvious. It will not be supported while TPX will continue to be supported.