Well it's the "new reality" for those QBs good enough and healthy enough to make it happen.
That's new and different in that a focus on health and fitness can empower a QB who has that drive
But I think the bottom line is that the lack of quality QBs in the league leaves the door open for QBs who make it to their 40s period.
Over the past 20 years there are maybe 10 QBs who, regardless of the number of SB Rings, are guys good enough in their prime to even consider playing in a sub-prime post-40
Top 10 NFL quarterbacks of the past decade | NFL Analysis | Pro Football Focus
So while this dearth of QBs creates a higher demand for older QBs, there's no way that will ever be the "norm" simply because most QBs are just mediocre in their prime - let alone in their 40s
There is no dearth of QBs. There may be an absence of an all-time great in the ranks of the younger QBs, but there are plenty of NFL level QBs.
Brady
Brees
Tannehill
Roethlisberger
Flacco
Dalton
Carr
Rivers
Smith
Luck
Mariota
McCown (?) - late bloomer, and probably not but arguable
Watson (?) - promising, but too soon to be sure
Taylor (?) - must be in right system, borderline at best, and he's definitely not a guy you build around
Kizer (?) - probably not, but too soon to write him off
Bortles (?) - Almost certainly not, but he shows flashes of what might possibly be brought out of him
In the NFC
Wentz
Cousins
Manning (though fading)
Bradford
Rodgers
Stafford
Brees
Newton
Ryan
Winston
Goff
Wilson
JAG (?) promising start, but too soon to tell
Bridgewater (?) - if he's actually back from his injury
Keenum (?) - depends on whether or not this stretch is a fluke
Prescott (?) - too soon to be sure he's not just a product of Elliot and the line
Trubisky (?) - too soon to tell
Palmer (?) - probably shot
and that doesn't get into the guys like Mahomes, who are being groomed behind others. The league is actually flush with NFL level QBs, because the likes of Brady/Brees/Manning/Rivers are playing well deep into their theoretical NFL dotage.