While it is true, irreversible removal of enamel followed by orthodontic movement CAN shift a midline, there is a concern that the teeth will STAY shifted. Moving a tooth 4 mm is one thing, and any "settling" after braces are removed is insignificant, up to 1/2 mm. This won't be noticed. ...
Congratulations on being close to finishing your orthodontic treatment! Since you have concerns, I recommend that you talk to your Orthodontist before having the braces removed. It is difficult to assess your overall treatment progress from the pictures, but it appears that the concerns you have...
If you had full or comprehensive treatment there should be no spaces left in this location.
Your orthodontists works for you. He/she should only take the braces off when you are both satisfied that the job is complete and the best possible outcome has been achieved....