So the Jagged Alliance 'franchise' ended when Sir-tech went under after JA2:UB. The rest were half-assed spinoffs by starving developers, trying to capitalize on the title.
Anyone can build maps and characters, but it's the AI that makes the game work. All of the spinoffs had horrible enemy AI, which killed those games.
Most of the hardcore JA fans don't believe the franchise is dead. It just needs some real money and manpower to make the game we want. I'm surprised, with the overwhelmingly successful reboot of XCOM, that a legit developer hasn't rebooted JA.
Hrm, I'd disagree regarding the AI here. Well...maybe the AI in the spinoffs was worse. But it certainly wasn't the strength of JA1/2 either. You could easily trap and execute them one by one. I'd say that the strengths are:
1. Authentic replication of real firefights (name one other game where interruptions can be interrupted or you sidestep with your character to avoid interruptions. XCom doesn't even calculate the trajectory and ignores all obstacles if they are not infront of the target).
2. Tons of freedom in how to tackle challenges. Do you want to lockpick the back door? Do you want to try to sneak in? Or do you just want to place dynamite and blast a big hole into the wall?
3. Lots of personality(humor) and Characters. The game did a lot of "unnecessary" stuff, like allowing you to get captured or to send flowers to the enemy. All characters have a "personality" and background. Tons of character voice lines recorded, only a fraction of people will ever encounter.
And I think these strengths also show why the successors didn't work out and why it's not as easy to make a successor to JA as it is to XCom. "Easy" as in "Risk Friendly".
Previously mentioned Reason 1 can make it complicated to completely understand the game and closes doors to a big audience.
Previously mentioned Reason 2 requires a very open world approach and lots of different systems which work together. Much harder (and more expensive) to accomplish than a more or less linear campaign with set missiongoals.
Previously mentioned Reason 3: Costs tons of money for rather little effect
So why does nobody make a new JA? Because it costs tons of money, it's very hard to do right, and at the same time the expected target audience is rather niche.
None of this is the case with XCom. XCom just had the issue of a potential niche audience. But they countered that by putting a bit more bling bling into the game (like kill cam) and simplifying systems.
And after these failures the risk of an additional failure and expectations are lower than ever before.
I'd personally not expect a real JA successor by a big company because they won't take the risk and not by a small company because they lack the money.
So we have to be content and hopeful with JA Elements being implemented into other tactics games. Like Xenonauts 1/2, Stellar Tactics, Graywalkers: Purgatory and the biggest resemblance so far I see in Urban Strife.
All Indie Games, and you cannot expect to get 70 characters with lots of voice overs, but at least indie developers will pick up on core concepts.