I wouldn't discount it, but I also wouldn't be so sure either. Less than 1% of hurricanes go annular and Rita has a very spiral pattern right now.
I'm gonna go out on a limb and say that Rita is one of those 1% type of hurricanes. But what folks need to put in perspective is that we have such a very very small sampling of data from GOM storms. We've got good data for the past 100 years, the 100 before that we have some written "professional observation" data, and before that we have little more than anecdotal evidence. The point is that we have no clue whatsoever (save looking at strata in various points along the Gulf Coast) what the cycle of storms is like outside 200 years. When it comes to 500, 1000, or 10000 year cycles, we are in the dark.