Well... I guess I'll go ahead and be the party-pooper.
You will never see a 2D Civ game come out in the future.
This is the way it is. Games cost millions of dollars to develop, market, and produce. Companies cannot stay in business if their products don't sell exceptionally well. Games sell because of hype. Graphics really, really help generate hype.
The Civ Franchise is an article of exception to this truth, or at least whenever it is treated by designers in that way, are problems with performance and AI weakness will go out the window
Ya we all know how it goes but that don't mean we all agree its good for the continued legacy. Are pleas are worth as much as any post here. Lots of em reflect a ratio constant to the number who want off this 'crash' course. Those who should be listening, would be checking here if they were. (though not crossin any fingers)
Your right, its all we can realistically hope for is less bugs and lag n less money in upgrades.
Once they get around the killer of great games, the graphics evoluton on all thta rot franchises, then wake up an focus their efforts on a AI Evolution instead, the Civ seriies would prove you wrong. Stores would move a ton of carts after the press acknowledges the fact CIv brings home the serious side again!. Players who fell by the way side to cartoonish "seasame Civ" land after so many years have all divvied for what they were waiting to hear.
You see Civ is unique in that it caters to thousands of people who don't play computer games just Civ1,2 3, and chess lol *mybe a couple games the love of Civ inspired them to try thats it. Remeber that Sci FI Auther who misssed his deadline cuz of Civ3 addiction I bet hes one of them.
Im telling you, Firaxis can still use 2d to carve its own category that replicates the demand, to a slightly lesser degree, of the timeless table classics like chess and checkers. I mean streamlined strategy that runs seamlessly for everyone. Ya More complex then checkers, still when your including all types of combat, economic, political, and religious options that pit you opposite an AI as intriguing as any opponent, devised to counter in every area. Invested in making you alternate on the plan for once, cuz to learning from patterns of player or other AI who attcks it AI could respond in attack in similar order (avoid non commitment fail seige manovers) and how its deviates from predicatablity to some degree could be pressed with the resources usually flowing inot programming like the fish jumping from the sea or Clouds that block your view.. These would be the steps that raise the game to 2009 standards.
Growth in the area of graphics? Sure but whats crucial is added variety of culture using civ3 style citys that also have more stages of growth. Having the city veiw back this time with a UP\DOWN (or 3d!!!) slidebar to show modders buildings and options for flik files attachments for a puff of smoke from Iroqious camp fire or the roof of a church glinting from the sun, small things, etc.
Imagine the mod Rise n Rule with a
City Veiw feature that enables you to collect a wonderful n' realistic assortment almost endless amount buildings and this time in tune with the population (not 2 skyscappers for city of 2 million residents), all the same with additionally designed wonders, let us showcase it all in one proud city if we want to.
The theme built on what Civ3's got. Use Land like startegic resources to add geographic stipulations to certain buildings like Mount Rushmore having to have mountains in city radius or The Statue of Liberty welcomig friendly's from across the ocean...not some big lake.

The possibilities are endless where to spend the money.
CIv5 being a step up from Civ3 engine would be the greatest game ever. Heck, fix the artys and half you would come running work on the settler sprees and the other half next -Ok now imagine those two fixs with what I mentioned on top as the tip of the iceberg then lay her down on a new 2d palette juiced with new modder flexabilty like Google earth skin graphs

Comon folks the game will cost 60$ at the most. CIv3 was a huge success. CIv3 as a template is the only thing to work from
Civ4 made a signifigant haul from the rep Civ3 earned. Look at the proof in Warkords dismal sales." We can't be fooled twice " is what "Desperate Housewifes the Game" beating Warlords its 3rd month out was telling them .
Like those players who've tried to replicate huge maps the likes of Civ3 size, Firaxis already knows why Big Polly really needs to go.
Going zoom zoom with higher lines of resolution is neat but Im saying 2d can set the franchise apart in exellence without going with the usual emphisis on 'improved' Graphics. The start of this course to "keep up" has so far pressed limits on growth in army sizes, world maps, # of citys, Civs at the same time, custumizing new civs and units...More setback, lack of detail to Advisors, view from afar, troop's fluid movements, pedia linkin, rapid response for menu switching...Missing Palace/throne veiw, unit variety culture selection. an on an on
Gameplay is the best thing a game can have going for it. Not fancy props that pop out at ya, Civ5 need more indepth stategy code that draws you in.