I think there would be some sadness, but maybe in Oliver's mind the legacy isn't all that great anyway.
The company has been at the base of a lot of bad things done by his father and mother and also being done to his family. I think he felt obligated in some respects to try to keep hold of it, and maybe in the future if he ever has the opportunity to get it back he can make it into a legacy that his family would be proud of.
But I didn't see much surprise on his face in the renaming scene. I felt he was sad, but mostly because he's watching Felicity helping Ray the way she was always going to help him. And no, that's absolutely not disloyalty on Felicity's part.