We need to be realistic in our expectations of him. He has been hyped (on here at least) to the extent that anything less than becoming a talisman would be a disappointment. Expectations should be tempered.
The positive is that he got plenty of games at Cardiff, and looked like he belonged at Championship level, without ever really standing out consistently. But for a first ever loan after a horrible injury, that is a relatively successful outcome. His technical ability looked above most of his peers, but seems to lack a bit of speed/acceleration to get away from his marker.
Next 2 years will be critical to his development. If we aren't going to use him, I'd rather he get another season long loan after a proper pre season, even as low as League 1. He's still so young and has played so little football that it will benefit him much more than being planted on our bench. Grealish, a player with a similar skill set and limitations did so and it did him no harm.