That program, which has been criticized for potentially encouraging asset bubbles, is also a centerpiece of Bernanke's legacy as a Fed chairman who used extraordinary means to save the economy and revive it after the financial crisis.
Another key Fed policy is forward rate guidance, and traders are watching for any nuance in how the Fed refers to that in its statement. The Fed continues to keep its target fed funds rate at zero, and convincing the market that rates will remain low for a long time, even with tapering, is one of the challenges Yellen will inherit.
"There were moments in his tenure in which your ATM card might not have worked," said Ian Lyngen, senior Treasury strategist at CRT Capital. "I think it's really, really easy to look smart when you're asking the question or criticizing, but there are a lot of hard choices Bernanke made. He helped the economy survive, and the biggest risk was that inflation would take off. … He made a bet and was willing to cover his bet if it went the wrong way, and it didn't."
(Watch: The Fed and income Inequality)
But, he said, "he may have created some bubbles we don't know about."
Lyngen said the Treasury market has already priced in the next taper and may trade more in reaction to emerging markets ahead of the Fed meeting.
"I think that [Turkey] will set the tone for risk assets, and the Treasury market will take its direction accordingly," he added.
A $15 billion auction of the new, floating-rate 2-year Treasury note also will be held Wednesday.
There are dozens of earnings reports Wednesday, including Boeing, Chrysler/Fiat, Novartis, Dow Chemical, Canadian Pacific Railway, Southern Co., Biogen Idec, Marathon Petroleum, JetBlue, Nintendo, Valero,Tupperware, WellPoint Health and Hess before the opening bell.
(Watch: The Fed and emerging markets)
Late-day reports are expected from Facebook, Las Vegas Sands, Qualcomm, Citrix, Lam Research, Murphy Oil, Fortune Brands Home & Security, International Rectifier, Vistaprint, Astoria Financial and Flextronics.
There are weekly mortgage applications, announced at 7 a.m. ET, and oil inventory data at 10:30 a.m.
—By CNBC's Patti Domm. Follow her on Twitter