To "Aflop 1"? 😄

Given what has happened with the multiple plant fires, I'd be surprised if we see it by next Summer. 

While the Challenger isn't being sold, they are making a two door Charger     The Camaro is in the shitty position of having the Corvette above it, so it's a redheaded step child. The Mustang is one of Fords Halo cars so it doesn't have to deal with that. 

I think some of the sales numbers of the S650 is Ford inflicted and not the market per say. If it wasn't profitable or at least breaking even, Ford would be doing something else or getting rid of it (though that would be highly unlikely)

On the contrary, it proved that an evolution model is cost effective and actually outlived  the competition 

The deaths of the Camaro and Challenger probably relieved some pressure on Ford to update the platform substantially. The Mustang is the last real pony car standing.

Someone PLEASE let Sony and Honda know that they still have time to rename this thing. 

Agreed, doing a mustang sedan that has a lot in common with the coupe is a solid strategy. Just in fleet sales alone, unless Ford gives the sedan a completely ridiculous price, I could see it being quite popular with police fleets as their chargers age out.    That's not even getting into normal consumer sales. Furthermore, if the day comes when Ford does decide to give the mustang a new, more flexible platform, I think there's a market for using it for some halo models as well. Like taking that same platform, and doing a cobra/Thunderbird halo product, or Lincoln variants of a RWD sedan or coupe. The kinds of high profit projects that could go a long way just on their own in terms of paying down the engineering costs for a new platform.    Flat rock can't build anything but cars. It's already set up to produce mustangs. Investing in it to build other highly profitable models riding on tweaked versions of the mustang platform feels like a no brainer. Much better than just leaving the plant at under capacity. You're just remixing a plant, and a platform you have to develop as is, so why not get the most out of it. 

To answer your question should Ford invest additional funds into the coupe and a sedan moving into the 2030s, I can't stress enough that the answer is yes. The mustang is Ford's gem, their crown jewel, and most important product without a doubt as far as reputation and iconic vehicles is concerned. Letting the mustang wilter and ultimate waste away would be the worst mistake Ford has ever made as a brand. Without a mustang coupe, Ford ceases to be Ford, and just becomes another car company.    It's worth noting that while the s650 isn't selling well, it's still not a failure, it's still the best selling sports coupe in the world. Walking away from that would be genuinely unforgivable. 

I feel like the only way the program can justify itself/upgrades long-term is to add another model like the sedan that shares most components (dash, interior components, front end, etc)....this helps them get the ROI back on these items despite lower sales per each type (i.e. if they used to sell 20k units of the coupe, now they're down to 10k units, if they're able to push out 10k for the sedan, they're back at the 20k overall total). Obviously there are still components unique for each model (coupe, convertible, sedan), but you're at least able to spread some costs across the volume of all 3.