The difference between McGregor playing Obi-Wan and this is that he was playing Obi-Wan at a totally different age from when Alec Guiness played him. So it wasn’t really the same role at all. Even still, he was a perfect fit in that his appearance, voice, and mannerisms were all uncannily similar to Guiness. On the other hand, we’ve seen Han at a younger age, not much older than the age this new guy will be playing him.
+1