Given some of the ETFs that have been discontinued, and others with low assets, it will take some innovative and useful new ETF products to prosper.

Some proposed ETF ideas of my own, that I am surprised have not made it to the market, include products similar to the idea behind Vanguard's Extended Market Index ETF (VXF), but applied globally to international ETFs. In other words, to have investment vehicles that capture everything other than the largest cap portion of an index.