That’s why SIG won’t win.
But, the AR15 will no longer be a military weapon either. At least here anyway.
I’d bet on a hybrid but fixed cased round (mild steel case head, metal or poly body, [probably brass/aluminum],dual purpose bullet [a la M855A1/M80 EPR bullet] and an updated progressive powder charge) over either a telescoped or caseless round.
The former works and is a logical next step up, the latter two have never shown much in terms of reliability and ballistic performance (internal, external and terminal) despite nearly 60-70 years of trying.
My gut says the AR platform will be with us for another 20 years, if not longer.