U.S. exchange-traded fund assets are expected to double to $2 trillion before the end of 2015, according to a new report.

The report, entitled "ETFs 2.0: The Next Wave of Growth and Opportunity in the U.S. ETF Market," and released on Wednesday by BNY Mellon and Strategic Insight, says that asset managers can tap into the vigorous growth of this industry with products that are passive, active or somewhere in between.

"The next wave of growth for ETFs is being driven by new asset classes, new indexes and new ways to use ETFs as tools for portfolio construction," said Joseph Keenan, head of global exchange traded fund services at BNY Mellon Asset Servicing.

Keenan noted the increasing sophistication of ETFs can pose operational and distribution challenges for asset managers.

"However, with detailed planning and a focused strategy, a variety of innovative exchange-traded products can be brought to market to effectively meet investors' needs," he said.

According to the report, traditional index-based ETFs are likely to account for a falling overall share of ETF assets as non-traditional and alternative funds grab a larger slice of the market.

Since the end of 2008, non-traditional ETFs have grown from 18 percent of the market to an estimated 30 percent of U.S. ETF assets as of March, according to Strategic Insight's Simfund database.

The BNY Mellon-Strategic Insight report predicts this trend will continue as investors become less likely to simply allocate their assets among growth stocks, value stocks, large cap stocks, small cap stocks and other traditional categories.

"Non-traditional ETFs will continue to increase their share of the ETF market," said Loren Fox, senior research analyst at Strategic Insight and an author of the report. "Commodity, leveraged, inverse, actively managed and hedge-fund-like ETFs are among the non-traditional ETF types that should see market share growth between now and 2016."

-Jim McConville