No. Grant can go away anytime the arbiter decides. The current master only has to give up control of the bus after GNT is removed *and* its latency timer runs out.
FRAME# and GNT# have nothing to do with each other. REQ# causes GNT#, somewhere down the line and a master without a GNT# must give up the bus somewhere down the line (after it's latency timer runs out and *it* parks the bus), but other than theat they aren't related.
Get the spec, or perhaps more easily understood, the MindShare book.