I just carried them forward to the current release (assuming they weren't resolved).  Its way more readable to have a list of "known limitations as of now" then to see a known limitation in rc1, then maybe its fixed in rc2.  But you have to parse the whole document carefully to know for sure.  For RC1 and RC2, etc its not important to know the known limitations for them as they weren't official releases.  We have a record of bug fixes which captures that info better.  Once we cut an offical release I won't do the carry forward trick.