I just realised something!
Remember that picture long ago with Matt and Shiro in it
Everyone was relieved because it meant Shiro was alive.
We thought in S3 we were going to get Shiro back. Even though we did, we got the wrong one. We got clone shiro, kuron, instead
Well, we are in fact going to see the real shiro again. How? Because the shiro in the pic above is the real Shiro
Why you ask? Because of this
Look at this shiro’s eye. Only the real Shiro’s eyes look like that.
The shiro that is with matt is OUR SHIRO
So this pic must be after Shiro returns and the clone shiro gets found out or Shiro did get transported to Matt somehow or the rebels found him.
If we go by the second theory, that means that when Pidge goes looking for Matt, she may find Shiro as well.