Just lost a ranked game, point B of volskaya industries where the white circle was completely full but on the last millisecond a reaper uses his wraith form and stops it, it's not overtime but why should this be allowed? they just switched to reapers and floated on, we couldn't stop them...

This should not be allowed to happen, at all.

Is there any plans to change this?

We used to have it so that things like Transcendence or Wraith Form did not interrupt capture progress but it felt really bad. Often times, you were playing a hero like Reaper normally and would instinctively use your ability and lose a match. In a lot of ways the game felt broken and buggy when those abilities could not delay point capture.

We are addressing Overtime in an upcoming patch but that still doesn't change how this feels in regulation time. We want to do one round of changes first and see how prevalent stalling still is and then do another round if stalling regulation time is still a problem.

The changes that Jeff Kaplan addressed is that overtime now increases the respawn time of both teams by an additional 2 seconds. In addition, the longer overtime is going on the faster the cooldown "wick" will burn down when the objective is no longer contested.