IMO the best hope for modernized Civ 4 is creating open source engine for it.
OpenMW and its spin-offs has worked out internal workings of NetImmerse engine, so the work does not seem as daunting as it may seem.
Civ 4 makes heavy use of scripting languages, so the only thing that needs rewriting is C++ core.
What it would mean:
- Civ 4 on any platform, including mobile devices
- better multithreaded performance
- no more 32-bit memory limits
- no restrictions on what mod can and cannot change
- fixing hardcoded bugs
Of course graphics improvements would not be as impressive as with professional remake / remaster - just an upgraded renderer and some better shaders.
That, I have to agree. I think its, realistically speaking, our best chance would be an open source port.
I see fanbases like the Fallout fanbase going all "Give us remake!"* meanwhile, the classic X-COM fanbase got off its ass and made Open X-COM - and now there are even some guys making a open source port for X-COM Apocalypse (which is a totally different engine).
With a open source port, we could finally get rid of all the engine limits hampering us. I am pretty sure that with that, we could make the best Civ-like experience ever done. And then, as long as Firaxis doesn't bother us (good ol' needing original assets to play the port AKA buy the damn game first solves this), and I doubt they will, we can do whatever.
*with the exception of Lexx who has done a fantastic job with the "Fallout Et Tu" project, which is a Fallout port to the Fallout 2 version of the engine.