"The entire process takes 12-18 hours. The 5AM NHC advisory noted the beginnings of it, so it likely began at 4AM today. Recon still shows concentric eyewalls but the inner eyewall is almost toast. The cycle will likely be completed by midnight or so."
So does that mean that it could strengthen back to a 5 by landfall?
It's quite possible. It's also possible it could begin another replacement right before landfall, though.
Very good chance Rita makes it back to CAT 5 -- she has a very warm eddy to cross, and her pressure is still very supportive of a CAT 5. HOWEVER, as she approaches landfall there is a good chance that the slightly cooler coastal waters, and interaction with land will weaken her back down to a CAT 4.
That said, her track will have a very big effect on her end strength. The waters off Galveston Bay are the warmest in the area -- if she tracks there she could retain much of her strength. A northerly turn toward Port Arthur/SW LA would get her into slightly cooler coastal waters.