But it should not be otherwise; else just make something else. It's tantamount to re-releasing Lord of the Rings set in New York with gangs and hackers (wizards), with the ring being an addictive drug formula...
The games were the sum of their parts... not ~some of their parts.
And you are incorrect [I would say], because mechanics are only optional methods; and they exist because of what they offer (each to their own strengths), and most often they cannot directly compete. Fallout cannot deliver what FO3 does, but neither can FO3 come close to the impact of Fallout.
(They are different /mutually exclusive methods; offering entirely unrelated ~different experiences.)
The problem with doing Fallout any other way, is that it could no longer excel in what it was good at, and cannot really excel with the current gaming fads ~while hampered with its previous baggage... So the result would be a hamstrung mess for either preference; and better left unattempted.
** There are plenty of turn based titles released even in the last few years, and slated for this year and beyond.
(Fallout 3 should have been among them ~even spearheaded them... but FO3 did not; seemingly was never intended to, despite being heir to a grandfather RPG franchise with a great reputation (to live up to!). )
FO4... who knows; but I would assume not, not if they stick to their TES formula for it. If they surprise us with a more strict and less forgiving title that blooms with story, and not just lighting effects ~that would be a [welcome] game-changer.
*But I am not sure they can.... I've no idea of the data costs, and how that would affect their open world simulation ~(that has to reset every so often); Fallout's design never had that problem to contend with.