Investors aren't expecting a turnaround in the slumping initial public offering market for another two years, a survey finds.

Of more than 290 venture capitalists, corporate buyers, bankers and entrepreneurs polled by KPMG, 79 percent said IPO activity won't pick up again until 2010, while 15 percent don't expect a rebound before 2012. Up to 12 percent said the market would never fully recover.

The downturn has already prompted many VCs to extend exit timelines by 12 months or more, as they wait longer for returns on startup funding, the survey found. Over the second quarter, not a single venture-backed company went public, the first quarter in 30 years without an IPO, according to the National Venture Capital Association.

The sharp downturn has market watchers warning of a crisis in the start-up community, as the credit crunch, weaker economy and jittery investors make IPOs a less attractive source of capital for new businesses.

"There is no question that economic and market conditions have dealt the IPO market a blow," Packy Kelly, a co-leader of KPMG's venture capital division, said in a statement. "These conditions have led investment firms to hold positions longer," he said.

The emerging greentech sector is expected to attract the bulk of venture funding in the years ahead, followed by digital entertainment, mobile and life sciences, the study found.