Exchange-traded funds track an index or group of assets but trade like stocks. The approval of one could bring in a wave of institutional buyers and, because bitcoin has a fixed supply, theoretically push up prices.
Hunter Horsley, CEO of Bitwise Asset Management, which submitted its own ETF proposal to the SEC in June, said investors shouldn't read into Thursday's deadline.
"An SEC filing hitting a deadline is a procedural reality — it doesn't change the odds of it getting approved, it just draws our attention to it," Horsley said. "Just because we hit the deadline doesn't necessarily give any indication that the SEC has changed its tune."
Struggling bitcoin prices jumped ahead of other SEC deadlines for ETFs this summer. The cryptocurrency rallied 20 percent, above $8,000, in late July on rumors that another ETF, proposed by VanEck, would be approved in August. That decision was later postponed by the agency.
This week, price moves have been more subtle. The cryptocurrency rose roughly 3 percent to a high of $6,858.61, according to data from CoinDesk. Bitcoin is still down more than 50 percent this year and more than 65 percent from its high near $20,000.
Brian Kelly, CEO and founder of BKCM, said investors are getting more cautious and have stopped betting big ahead of these SEC deadlines.
"My view is still [that] this does not get approved tomorrow, but I feel we're making large steps and getting closer to it," Kelly said. "There's a better chance this gets approved than anything else."
One reason the ProShares ETF might be more appealing to regulators is because it's based on futures trading. The agency has cited the lack of regulation in bitcoin exchanges. But bitcoin futures trade on the SEC-regulated CBOE.