There's not a ton written about this that I can find, but cracks are appearing in the US military's plan to replace the M4 with a heavier battle rifle designed to defeat body armor. Sig Sauer, which also holds contracts for the current generation pistol and LMG, won a contract last year to also provide the US military with a new rifle. This rifle is to be called the XM7. The civilian equivalent is the Sig Spear. Calling this thing an assault rifle is a bit of a stretch, as it is very heavy and uses heavy ammunition. It turns out that the rifle is failing to penetrate modern body armor without the use of tungsten bullets. Also its reliability is questionable.
I can invent armor defeating next generation weapons if I'm allowed to use a pipe and some other household products.
Either way, I think red-dot sights have done more to advance gun tech than any material or mechanical advancements. Just getting the bullet to go where you want it seems as important as whether you can overcome armor or cover.