Ozone is depleting, that is true, but gasses are free to move. Why don't they cover the hole, and if they are covering, then there will be a change...

The ozone layer is that part of the atmosphere that screens out potentially dangerous radiation from the sun, such as x-rays and gamma rays.  A hole in the ozone layer was discovered, caused by the ozone combining with compounds called "chlorofluorocarbons," or "CFCs", for short.  You are confusing the other gases in the atmosphere with the chemical makeup of ozone.  Yes, there are other gases in the atmosphere, such as oxygen that we breathe, but the chemical makeup is totally different.  Oxygen we breathe, also called diatomic oxygen, is O2 (two atoms of oxygen), whereas ozone is O3 (three atoms of oxygen).  So it is not as simple as allowing the regular oxygen to drift in and fill in the hole.  It is doing that already, but diatomic oxygen does not have the same properties as ozone, so it does not serve the same function.  A reduction in the amount of CFC's being released into the atmosphere project to have the ozone layer hole being repaired in about fifty years.