Should i care about replication traffic, generated by group policy templates central store? Do templates, stored there, replicate with client machines?
The templates stored in the SYSVOL (both old-style ADM templates and new-style ADMX templates) are not replicated to client computers. What you're probably thinking of, when you're thinking of client computers, is the behavior of editing a GPO with updated ADM files on a client computer. Quoting http://support.microsoft.com/kb/929841:
In Group Policy for versions of Windows earlier than Windows Vista, if you change Administrative template policy settings on local computers, the Sysvol share on a domain controller within your domain is automatically updated with the new .ADM files. ... In Group Policy for Windows Server 2008 and Windows Vista, if you change Administrative template policy settings on local computers, Sysvol will not be automatically updated with the new .ADMX or .ADML files.