I second this.
I think Messi will still be very helpful to the team in the next 2-3 years because of his special skills.
He might not run much anymore, but his passes are still as sharp as laser. Once he gets the ball, he can control and maneuver it very well, it is near impossible for any opponent to take the ball from him => he can help us to cope with strongly pressing opponents.
I mean, he can still play at a lower position, perhaps in the upper part of the midfield, a position which does not require much stamina. He will be like a brain, coordinating Barca's attacks.
To recap, in the next few years I believe he is still second to none regarding the above mentioned skills. So it would be a waste if we let him go after this season.