Him leaving sends out the message that Koeman and the club will not be messed about by Barkley & his agent. That if he thinks he can 'play' the club by runnning his contract down to summer 2018 and then walking free, then he & his agent are wrong.
I prefer to see a strong club taking no crap from any individual player and working in the best interests of the team and the club. That is what this whole contract issue is about, and it lets the rest of the first team squad see clearly where the Manager's interests lay, and also shows to potential players coming in that the Manager and the club have a clear vision of how they conduct business, i.e. professionally. Not letting one highly paid, promising player (but something of a [Poor language removed]) dictate to the club.
I like what I am seeing from the club over this issue...