No, it won't work out of the box.
Best practice would be to check, which version is already installed on 6.5 (rpm -qa), to remark (or delete) those lines, which are not required and start the script.
You have to tweak the version check.
And leave out the secure mail contrib, as this is already included.
Since SME 6.5 never got out its RC status, I stopped testing the plus script with SME 6.5RC1.
However you may try my latest script for 6.5, but I cannot remember, if it worked like expected, so take care:
http://sme.braunstein.de/update/sme65plus.sh(contribs will always be installed with this script and I left out all warnings of the 6.01 script)