I come at this from a different perspective. Steel and aluminum alloy framed pistols have had multiple decades of developmental time put into them.
There is not likely going to be any "new" steel or alloy framed pistol that is going to appreciably improve upon the 1911, BHP, CZ-75, SIG-22x or the Beretta M92. Steel and alloy has hit diminishing returns design wise in duty arms. Even then, we have seen some metal innovation at the pocket end of the spectrum with Kahr and the Rohrbaugh R9. Polymer has its design limits at the lighter end of the spectrum because shootability and limited flexing become very important and that requires some stiffness and some mass, which metal provides more straightforwardly than polymer can.
OTOH, polymer is really just getting cranked up. H&K was first. Glock popularized. Walther innovated. Dozens of companies experimented. Lately, things have gotten interesting. Glock's patents are expired, H&K is getting better rather than worse, the M&P arrived, the XD morphed out of the HS2000, SIG has kept experimenting and even Beretta's plastic has a cult following. It is extremely likely that all future duty sized weapons will be polymer framed unless a breakthrough in metals is achieved that gets machining out of the equation.
Liquid metal technology that eliminates the drawbacks of casting could be that innovation down the road, but it isn't cost competitive yet to be tried in a frame application. It has some promise though:
An amorphous alloy that can be cast into near final form without the weakness or bulk of traditional castings due to higher strength and elasticity could conceivably give polymer a run for its money in the future, especially if the innovation of design in plastic framed firearms has flamed out.