What will be hot for 2015 IPOs?

Thanks in part to a massive $25 billion offering by China's Alibaba Group, the U.S. is on track for its biggest IPO year since the technology bubble in 2000. With another Alibaba-sized deal unlikely, what will drive the market next year?.

One promising new area is nonbank financial companies similar to LendingClub, which fills the role of traditional banks that don't usually to lend to certain types of borrowers. LendingClub plans to price its IPO on Wednesday. Its valuation could be $6.5 billion if it sells shares at the top of its range at $14 each.

Read MoreHow LendingClub aims to end banking as we know it

Jack Ma of Alibaba Group during the IPO at the New York Stock Exchange, September 19, 2014.
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Jack Ma of Alibaba Group during the IPO at the New York Stock Exchange, September 19, 2014.

Clearly, the company is a fraction of the size of Alibaba, which priced at a market capitalization of $169 billion. But similar nonbank financial companies could be one of several big IPO drivers in 2015.

"Nonbank financials will continue to be active," said Philip Drury, co-head of equity capital markets for the Americas at Citigroup. He added that he already expects "a couple" of nonbank financials will want to go public in 2015. He said such companies continue to address "an explosive market" that traditional banks aren't filling.

Drury expects new issues to come from a diverse group of sectors. While there are a few good-sized technology companies planning to go public in the next few months, they aren't the size of Alibaba, he said.

As for the total U.S. IPO market, 2015 may be roughly the same size as 2014, said Douglas Adams, Citi's other co-head of equity capital markets for the Americas. That prediction, of course, assumes that equity markets remain relatively stable, he said.

The U.S. IPO market has seen $92.5 billion in total volume in 2014, according to Dealogic. That's the highest level since $105 billion in 2000.

Unlike 2000, when technology drove the majority of new issuance, the recent boom has been more diversified. In 2014, technology accounted for 42 percent of new U.S. listings, with finance at 18 percent, health care at 10 percent, and oil and gas at 9 percent, Dealogic said.