SVN for Beta?

I’d like to update to the beta version of 2.7, but have been updating (stable versions only, so far) via subversion and I don’t see 2.7 in the list of tags. Is it possible to update to a beta version using svn? Or if I manually update, what happens then? Will I kill my install? Ruin my future ability to use subversion? (Which wouldn’t be the end of the world… I just need to know what to expect so I can deal with it.)