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DCS and FSX are both at the start of development regarding the way they look to be going - Falcon 4 is being developed still.
However if you are interested in the Vietnam conflict and that era then don't hold your breath that any of the above will provide what you need - you mention the content thats available for SF2 that has been created over the past 10 years. Well someone has got to do all that again for the above sims - and TBH their focus seems mainly to be post 1983 (there is an F-100D, F-104, A-7 in 3rd party dev).
But then SF2 has this:
Also if its clickable all functioning 6DOF cockpits with accuracy - they take forever to do - DCS has only got the A-10C and the choppers, Falcon has got the F-16C B50/52 - (and an FA-18C on the way) - however its not only the development time for these - who out there with a job has time to learn more than 2 pits like this - when you want to fly different jets then FC3 and SF2 are perfect - you still get a 3D accurate pit and unique FM - but can switch between the jets easier and spend time on tactics and action.
Thirdwire have started porting the titles onto mobile Operating Systems (Android, iOS, Windows 8) and is trying a freemium type business model - so for the time being the current Windows version looks stagnent - and cant say it will come back if the new revenue streams produce more money. Even the Windows 8 version might just be a cut down arcade game like the other mobile apps.
If they stop there then so what - I have First Eagles 2 that hasn't had a patch in years - but its a stable game and you can just add mods to it without the fear of having to lose those mods when you need to upgrade to another patch.
I think I'm running SF2V with the Gold mod add on and my own mods at about April 2012 so I get populated Carrier decks and carrier groups and it seems to be okay - even though I don't like some of the later changes that were made.
SF2/E/I are at Nov 2011 which was a stable patch - and SF2NA is merged with another SF2E at the latest patch.
So the positive thing about SF2V not being developed (if thats the case) is you can add all the mods you like to the game and not have to worry about the next patch breaking everything.