This ETF isn't as heralded as its larger relatives, but it's one to watch this month, and it could be a star next year.Issuers of exchange-traded funds (ETFs) are nothing if not inventive. One of the ways they find success with new products is to tie them to established, successful funds.The Invesco NASDAQ Next Gen 100 ETF (QQQJ +1.03%) is an example of that phenomenon. This ETF follows the Nasdaq Next Generation 100 Index, which is equivalent to a "junior varsity" of the Nasdaq-100. In essence, this fund i ...