I don't think there will be a crash. If Bitcoin replaces fiat, I would expect all fiat currencies to hyperinflate. This would actually make stock prices go to the moon, in nominal terms. Of course, if you adjust for inflation, they will probably go nowhere on average. Individual performance will depend heavily on how well they deal with inflation. This is what has happened to stocks since the dot com crash, if you adjust for inflation.
Discussion
Look at stock markets in Argentina, Turkey et al, worthless in real terms.
Stocks have been monetized as a trend to avoid debasement, so one would assume the stock market in aggregate would decline overtime as people rotate out into Bitcoin.
I don't think most people will realize what's happening until it's too late. They will just see the number going up and think they're getting rich. If they're lucky, whoever manages their portfolio might put some in bitcoin, but they won't liquidate stocks to buy. I am assuming hyperinflation, though. If that doesn't happen, you might be right.
Upward crash
Iβm talking about real value, not nominal. In that sense you are correct