I discussed upgrading Subversion to version 1.4.x with DreamHost. Their policy is that they only use the stable Debian packages except in rare circumstances where the stable version is very out of date. In that case they will use the backports.org version.
They didn’t say no but I definitely got the feeling that it would be more likely to happen sooner if they got more feedback from their customers.
So if you would like to see Subversion upgraded to version 1.4.2 I suggest filing a support request.