Oil could also be a factor for markets Thursday. West Texas Intermediate crude futures rose 1.5 percent to $45.50 per barrel Wednesday and then rose above $46 in late trading when American Petroleum Industry data showed a sharp, unexpected plunge in inventories of both oil and gasoline. U.S. government inventory data is expected from the Department of Energy Thursday morning.

The European Central Bank president speaks ahead of the Wall Street open at 8:30 a.m. EDT, after a much anticipated ECB meeting statement at 7:45 a.m. Speculation about what the ECB will do has been swirling around the globe, including talk that it could buy bank bonds and even equities ETFs.

The Fed can take the day off Thursday. All eyes will be on Europe's Central Bank (ECB) chief Mario Draghi.

Traders around the world are watching a string of big central banker meetings this month, with the ECB and Bank of Japan (BOJ) easing at full throttle, while the Fed takes the opposite path - toward a rate hike. The ECB is not expected to move on rates Thursday, but it could extend the time frame for asset purchases past next March and maybe even announce new assets to buy.

"I thought the ECB was going to expand the purchases to other securities. It seems that we're prone to some disappointment from Draghi tomorrow. He's not going to pull another rabbit out of his hat, and maybe yields will go higher tomorrow around the globe," said Chris Rupkey, chief financial economist at MUFG Union Bank.

The Fed and Bank of Japan meet later in the month on the same days, Sept. 20 and 21.

The ECB is the most anticipated event for Thursday's market. There is a Fed speaker - Kansas City Fed President Esther George at 2 p.m. at a conference on exploring financial resiliency and mobility. There is also little data with weekly jobless claims at 8:30 a.m. and consumer credit at 3 p.m.

"Everyone now is of the opinion that the Fed's going to take a pass" at its next meeting, said Wedbush Securities managing director Steve Massocca. "So are we waiting for the September employment report on the first Friday of October? Is that the next piece of news that matters?"

Traders may be more immediately watching the behavior of Apple stock, after it defied its usual pattern of selling off on days of iPhone announcements.

According to analytics firm Kensho, Apple stock has ended the day in the red 80 percent of the time after an iPhone announcement, then traded higher the next day 70 percent of the time, for an average gain of nearly 1 percent. But Apple shares gained 0.6 percent Wednesday after Apple unveiled the iPhone 7.

"Apple could be something traders watch," said Scott Redler, partner with T3Live.com. "Historically it goes up the day after they have an announcement but today it didn't go down, it hung in there. Does that mean it goes down? Does that mean tomorrow's a strong day. I think traders will look at it… I went home long because I liked the way it acted."

Redler said it's been positive that tech stocks such as Amazon.com and Facebook have broken out to new highs.

"I think you still have to be constructive on the market. Although the indices are choppy, there's been an upside bias. Although we haven't broken out to highs for a month, there's been constructive stock action," Redler said.

The S&P 500 closed a point lower Wednesday at 2,186, but the Nasdaq closed at an all-time high of 5,283, up 8 points.

The U.S. presidential election is becoming a bigger talking point for markets, so traders will also watch for reactions to the separate appearances of Republican Donald Trump and Democrat Hillary Clinton on NBC on Wednesday evening.

"The election is tightening, but no one thinks Trump is going to win. The popular vote looks close but when you look at the electoral college, it's not close," said Massocca.

Redler said he's watching the biotech sector which has become a proxy for perceptions about Clinton's success, since she has caused sell-offs in the sector. "Every time Hillary looks bad, they sell off. When she doesn't, they buy," he said.

Disclosure: NBCUniversal, parent of CNBC, is a minority investor in Kensho

