1. It could be a simple retest of the breakout point - something that happens quite frequently with breakouts. If this is true, then we would expect the market to rally tomorrow and eventually take out and close above today's high.
2. The market can move back inside the flag formation and end up being a bull-trap eventually moving below the lower trend-line.
3. And, of course, the darn thing can sit and hang out there, trading on both side of the middle of the flag, creating a broader trading range and a larger consolidation in preparation for a bigger breakout.
One final note - if this market closes above 63.62 (basis the July CME contract), the downtrend would be over on the daily charts and a new uptrend would in place. Given where this market closed on Tuesday, a bounce to take out that level would not be unexpected right now.