I propose to leave this for 1.6, I don't expect so many new files in 1.5 so the advantages would not be so many. On the other hand after 1.5 and the xml merging this would be the right time.
Is there any reason *not* to do it now? As a matter of fact, I do not see unmerged branches as a big problem. Since there are only filename changes, one can 1. update branch with trunk 2. produce a patch for the trunk with 'svn diff' 3. sync with renamed trunk 4. manually edit the patch, globally replace .C with .cpp 5. apply the patch to the branch. I can see at least one advantage of this: do it now and we do not have to bring this problem up the tenth time. Bo