Duty time limits, as you are likely now aware, are a significant regulatory issue. Fatigue was already No.2 on the NTSB "Most Wanted" list 5 years ago.
So I don't necessarily agree that it is going to take over as the party pooper. Objects with big blips on the radar screen tend to get meticulously vectored. Not necessarily solved, but held within limits
I think it will be have to become a party pooper before change occurs. Perhaps it may be true in some places, but I offer the comment that duty time limits are
not a significant regulatory issue in Canada and further, having just been involved with others in a change process to the Aeronautics Act regarding protection of safety information and seen the process first-hand, there is no taste for, or interest in change either there or in the CARs. The CARAC (change) process is absolutely glacial. Whether it is responsive to "studies" or not, is an open question.
An airline crew in a Canadian-registered airliner can legally be on duty for up to 23 hours. It's actually twenty hours but an "unforseen circumstances" definition in the regs permits crews to "decide for themselves" if they wish to continue. You may guess what airlines do with that freedom.
The twenty-hour limit is permitted if the aircraft is fitted with an SAE-specified bunk (most are not therefore legal), and prone rest is possible, and there is a third crew member. There is no regulatory mention or requirement of a fourth crew member.
While lobbying parliaments and congress has some effect, airline pilots have been forced into changing flight time and duty regs principally through collective agreements, spending negotiating dollars on coming to terms with lax duty day regulation in Canada. Under the heading of "regulatory impact", the CARs (Canadian Air Regs) duty day limits are what the ATAC, with the support of IATA, were able to lobby (negotiate) for and implement on behalf of the airlines during the initial move to the CARs in 1996, (a time, incidentally, when a great deal was already understood regarding human performance and fatigue levels).
Regardless of length of duty day and keeping the above regulatory provision for a third crew member on long-haul operations, a fourth crew-member is only the result of a private, collective agreement between airline and association and where it has occurred was extremely difficult and contentious.
Crews are left improving safety not through lobbied regulatory reform but through collective agreements, an entirely inappropriate arena for such limitations. Duty days for most airline pilots in Canada are lower than these CARs limits because pilots' associations, not airline managements, comprehend the safety risks in high fatigue levels. Long Haul Operations are not dealt with in the CARs except as described.
"Fatigue" issues may be on the radar of some and are the subject of many studies and papers, (I've seen Drew Dawson's work and discussed with him during presentations the notions of using FDA information to assist in studies - much would have to be done to design/facilitate such a study), the subject remains like talking about the weather - nothing is done about it. While it may be polemical to state that Canada is the Monrovia of the flight time - duty day regulatory world, there is no sign whatsoever that Canada's flight time/duty day regulations are to change any time soon - the ATAC lobby is too strong.
Even though we know differently (and I have done enough Hong Kong - Vancouver's with only 3 crew members to know), the difficulty in most cases is, before the accident, "fatigue" is not a demonstrable impediment to safe flight regardless of individual pre-flight details. There is no causal link which can demonstrate with the same strength of an MEL item, higher risk and the clear need for mitigation. Such support must come from knowledge already gained and, as lomapaseo states correctly, turned into a meaningful outcome. There is always the "unforseen circumstances" escape clause and there is always pressure to use it.
Unlike FDA Programs which may point to trends of increasing risk, no such "program" or technology (despite some promising entries) exists which may indicate that a pilot or a crew is sufficiently fatigued that action is required - it is a nebulous "human factor" and remains in the kicking-tin area rather than in pre-emptive areas of flight safety work. "Successful" approaches to commercial viability and fatigue risk management mean that crews keep flying until there is an incident or accident - the only measure of "proof" even today.
So yes, it is taking a long time to recognize fatigue as a real factor in accidents and government regulatory bodies and industry are becoming "more aware" but from where I sit, there is not the slightest sign of steps towards practical recognition and subsequent mitigation in terms of regulatory support and change.