Here's my take on it...
If you were to look at the growth of NFA sales as a graph, you'd have the average increase steadily rising for the past 5 years.
This relatively straight line is interrupted by brief spurts of panic buying every time 41P made the circles.
When 41F finally goes into effect, you can expect a plateau to form right then and there, as the majority of people who are buying NFA have already been doing so, perhaps exceeding their means to get in before the deadline, and will stop for a time.
This overshadows the much smaller growth of sales by people who haven't bought any NFA items to date because of cleo signoff and however else 41F is supposed to help.
I've bought far more NFA stuff than I ever expected to simply because I didn't know how 41P/F was going to pan out.
Certainly a large percentage of NFA sales the past year or two has been a direct result of people with the same mindset.
I still have that mindset to a point, actually...I'm trying to get as many F1's through the efile system because I doubt the average NFA owner will have the chance to F1 anything online for the foreseeable future with all of the new filing requirements.
However, it won't take long before the people who stopped buying before 41F will start buying again.
It's not likely that they'll just stop buying cool things because they need fingerprints and photos, they've already resigned themselves to all the other overbearing requirements for NFA ownership, so they'll eventually resign themselves to prints/photos.
Given a few months, the plateau will once again revert back to an upward trend, perhaps not quite as upward now that there are more requirements to meet and less spontaneous/sale purchases.
I honestly don't foresee any significant or quantifiable increase in NFA sales, but the possibility that it'll have the opposite effect is very possible.
Ask yourself these questions...
Have you ever heard anyone say anything similar to this: "Well I'm just going to wait until 41F goes through before I start buying cool things, I couldn't/didn't want to buy them before with a trust"
Have you ever heard anyone say anything similar to this: "Well I'm just going to buy all of the cool things now before 41F goes through, I can't/don't want to buy them if I have to get fingerprints and photos"
Chances are, you've heard a lot of the latter, but probably never the former.
The bottom line is that people are still going to buy NFA stuff regardless, but I do think it may put a curb on much of the impulse buying for cheaper items like silencers that are used or on sale.
Machine gun market will likely be unaffected entirely for the same reason...
Someone who couldn't have been bothered to get a trust in order to bypass CLEO certification and get what they want is not the kind of person that is going to buy a $10-20K MG once CLEO certification is done away with.
Likewise, someone who is dead set on spending $10-20K for a MG won't really care what kind of steps they have to take in order to get one, so 41F won't change the MG market.
Really, the only actual positive outcome from 41F is the ability to stick it to an anti-gun CLEO without a trust, and in my mind that's not worth the extra hassle and burden on the rest of the NFA community.