You may be able to deplane under the following circumstances:

1. Your arriving flight arrives very early.
   
2. There is a crew change and the crew will be late delaying your departure.
   
3. There is a maintenance issue that will delay the departure.

But, I would stay on the plane anyway or at least not leave the gate area. Just three days ago, I was waiting to board my flight and they announced an hour delay due to a maintenance issue. Many left the plane and gate area to get food and such in the terminal. About 10 minutes later, the maintenance issue was resolved and boarding was started. People were away from the gate, in bars, standing line at eateries and other things. There were people that were not in their place in line. It was a mess. Our flight was already an hour late, and losing another hour was not making anyone happy, so they started boarding any way they could. Some people had marked their seats and some had not. The marked seats were respected, but a lot of people were not happy that they had lost their seats or place in line.