airsoft has a lot more flexibility in terms of design, perhaps we will find the next best thing before they do.
? nah. The CM-16s that everyone buys are the same thing TM were putting out nearly 30 years ago. People don't want innovation in airsoft people want cheap (which is fine) and the people consistently get what they want - supply and demand. The money spent on airsoft worldwide is a tiny percentage of what is spent on firearms just in the US and just on the civvie market, let alone the 10s of millions in the military.
As above, firearms are absolutely at a plateau and if you buy a top of the line AR (or 416 or SCAR or X95 whatever) in something like .224 Valkyrie (and I'm talking very vaguely here, there are thousands of cartridges on the market) then that is as good as an assault rifle can get right now, application dependant. Caseless ammo was never made to be good enough, they might make part-plastic cases work to lower weight a bit, then in some 6.Xmm calibre with a quality variable optic, that's as close as you'll come to the 'perfect all rounder' rifle that's decent at close range and long, taking in to account barrier penetration and armour and non-armoured targets, recoil, capacity etc etc etc ad nauseum. Guns like that would be utterly wasted on most of the world's population though, that's why the AK is the most popular thing, it takes rough treatment and low maintenance in its' stride to a greater extent than the likes of the AR, L85, G36 and most other guns that shoot tighter groups than equivalent AKs.
I think bullpups have a lot of value in military service but they're going to die because they're not being made anymore realistically speaking, definitely not compared to the 70s and 80s. British small arms manufacturing is gone, as is French. The manufacturing power houses that are left (and you can count them in one hand in terms of factories that can outfit large armies) aren't getting big sales of bullpups, so they're not pushing their development. On the flip side, HK can't churn out 416s fast enough. There's a few small exceptions like the Tavor, aussie rifle and the Radom MSBS (which is only a bullpup half the time) but the FAMAS is being replaced with a standard layout and when the Americans adopt 6.X it will bring a new gun which definitely won't be a bullpup; that in turn will hugely influence many other countries. We'll get a standard layout after the L85A3, a lot of the nations using the AUG right now are/will go back to standard layout.
Airsoft wise, if you buy a full-ambi AR you can get to literally every control without even adjusting your shooting hand and bullpups are of little value since barrel length makes so little difference to a BB compared to actual bullets. It's also a self fulfilling prophecy because even if the AR wasn't a good gun, it's what is made, therefore it's what is cheap, therefore it's what people buy, so it's what other people see and what they see influences what they buy and what they buy influences what gets made.