to me there are different ways of interpreting the question. the most obvious way is to answer just what you asked: do we need a new stadium? the answer is no. the stadium is structurally sound, has a new envelope (both cladding and roofing). it has amenities required such as ample suites, total capacity, lounges, flexibility of use, etc. the interior finishes are not in disrepair. new orleans saints dont NEED a new stadium.
if the question is to be read with the possible implied meaning of do we need a new stadium.. to keep getting superbowl periodically?
in my opinion the answer to that might be yes. NFL seems to be more willing than ever now to not be limited geographically, and past few years have suggested they will go to where there is a newly built modern stadium. of course, this isn't the case year in and year out but it does seem to be a trend. LINK
i have to think that if new orleans built a brand new stadium the superbowl WOULD come whereas it might not come (or as often going forward) otherwise.
possibly leads to follow up question: is the "ensuring" of a superbowl via a new stadium reason enough? i cant answer this as i am not a financial guru or anything like that (im an architect). in my humble opinion, i feel that alone isn't sufficient reason right now to build a new stadium.
the superdome is highly unique, as you all know, in its longevity of "style". look at other NFL stadiums which have been abandoned/torn down/replaced. its subjective - but they were "ugly" and/or in some way dysfunctional. the superdome is still a pretty darn nice facility (thanks to the millions spent on its upkeep and renovations). its location is also still extremely ideal in my opinion. it's not a suburban stadium (which was a trend for a while, and seems to have backfired in many cases).
if they were to build a new stadium i cant imagine it having the lure the superdome has if it was built in a suburb. if it was built downtown it would be a burden. im sure downtown sites could be found, but then you'd be left with a huge superdome that presumably would no longer be used for football bowls or much of anything else except for a few concerts and monster truck rallies. if they demolished the superdome i think that might be challenging too because of the huge cavity it would create in the ground (fill is very expensive!!).
for better or worse i think we need to all embrace the dome and run with it for the foreseeable future - with or without superbowls.