As someone who does not play JRPGs I can't honestly remember when RPGs were mainstream in the first place. Sure, TES and Witcher are now mainstream, but even in period of Interplay's golden era, with Baldur's Gate, Planescape: Torment and Fallout 1/2, they were not mainstream. Sure, (almost) everyone knew of Diablo...but then again, Ultima was never mainstream, Might & Magic or Wizardry as well. RPGs, at least of C and W variety were always semi-niche products at best.
That said, since that sort of RPGs are not only still being made, but in sort of a second renaissance, I can't really say they are dead....but not mainstream, since they've never been that to begin with.