Samba is removed from Lion. How is the role of auto_master changed
Mac OS X never used Samba's SMB client. Mac OS X has always used an SMB client implementation based on Boris Popov's smbfs for FreeBSD. I don't think that's changing in Lion, so its relation to /etc/auto_master probably isn't changing.

As for the SMB server side, Samba is surely being replaced with a different SMB server software package.