In an interview with IndieWire, Mark Frost, David Lynch's Twin Peaks co-creator, said "I haven’t decided yet" with regards to Twin Peaks season 4. Lynch himself was noncommittal on the issue in September during a talk in Belgrade, Serbia.
There is something concrete (well, paper) on the way for people going through withdrawals since the series wrapped up its long-awaited return: Mark Frost's book Twin Peaks: The Final Dossier is due out October 31st. You can pre-order your copy today at Amazon.