The markets are expecting a very impressive QE, a la United States, a la Japan. Some investors may be playing both sides, and by that I mean playing for a big move. If they do come down with a big package, global markets will rally strongly, if they don't do much of anything, you could see markets fall apart," Nolte said.  "There's a huge amount of anticipation, and a lot of volatility around this ECB decision on Thursday. It'll be a combination of what they say they're going to do, and their intentions after that," Scott Wren, senior equity strategist at Wells Fargo Investment Institute, said.  "I think the ECB will act next week, and make some type of announcement. But the market is likely to be disappointed by the magnitude that the ECB initially says they're going to do, as the market would like to see a trillion. Let's say they come out with 500 billion, and some sort of statement of more.  Switzerland's central bank upended markets Thursday by removing its cap on the Swiss franc versus the euro, with the action viewed as a preemptive one to shield its currency from pressure should the ECB make a move.  "I suspect (ECB President Mario) Draghi gave a wink to the Swiss National Bank and allowed them to get in front of that, the question mark at this juncture is the order of magnitude. The market is vulnerable to an underwhelming response. The key, basically, is trying to restore the balance sheet to 2012 levels, so we'd have to at least have to see 1.3 billion euros," Luschini said.
Earnings and economic data all take a back seat to the European Central Bank in the week ahead.