Others aren't certain that the selloff marks a real shift in sentiment. "The market is just wanted to take profit when it can," said Simon Ip, director for fixed income at Credit Agricole.
But he did note that his firm has generally pared down its exposure to the high-yield segment for some of its different portfolios. "The yield spreads are already quite tight [for all bonds," with high-yield only attractive on a relative basis, Ip said. "But you shouldn't be out completely because that's where you earn a bit more yield."
Read More About those forecasts for bonds to drop…
Some don't expect the bond selloff will extend much further, even as the Fed appears set to tighten policy ahead.
In previous years when the Fed tightened – 1994, 1999 and 2004 – the average outflow bottomed at around 10 percent of assets, Deutsche Bank said in a note last week, adding that the selloff since July comes in at around $29 billion, or 4.5 percent of assets.
"To be sure, 10 percent is not a magical line in the sand, and all arguments how this time is different and unprecedented could find their reflection in investor expectations," the bank said. "Historical evidence provides limited support to such heightened expectations however."
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In addition, private equity may ride to the rescue if the selloff worsens, Deutsche Bank said.
"The private equity industry has raised significant amounts of assets with opportunistic credit mandates, which could be deployed rapidly if the market found itself meaningfully dislocated," it said. "This capital is locked in for a number of years, and it is patient in a sense that it does not have to track any given benchmark aside from a goal of delivering positive absolute returns over its full life investment horizon. This makes it a high quality substitute to fickle retail assets or dealer inventories."
—By CNBC.Com's Leslie Shaffer; Follow her on Twitter @LeslieShaffer1