The point you make is essentially right, he would jump at the chance to play for Barca's first team. I am not convinced that is on the horizon yet, even less so in January.
Like most football fans we tend to overate our players. Barca moved on Sanchez because he wasn't good enough for their first team. It gives an indication of the ability of their front 3. In honesty, Suarez, Sanchez and Messi remain on a different planet to Deulofeu. I can't seem them moving any of them on to give him a chance.
I think for Deulofeu he will be reluctant to move back unless he sees a chance for him to play games. I can't see that this season. Going back to being a squad player, just at the time when a consistent run of games is starting to show his development would be very foolish and I think he grasps that.
We also benefit from Enrique being there who doesn't fancy him and won't want to break up the front 3 mid season. In the summer it might be a different picture though.
I suspect if Deulofeu can show the consistency across a season there may be some movement this summer. All the times he remains an outstanding prospect I can't see it though, they currently have 2 or 3 teenagers who are as talented as Deulofeu was at the same age. It would be silly for him to go back before he can really demand a first team place on merit not on potential.