I just think the cupboard is so bare that we will have to play him for 3 years or there abouts despite his failings. Unless we go out and find another Chapman type pickup because its unlikely we will find a Hurley but we may find a Gibson if we're lucky. What is most likely is our next KPP Backman will be recruited, hopefully we will find the next Harry Taylor at pick 6 in the draft this year. But that player will take 3 years to get to 50 games assuming he gets to play.
If you project out 3 years then Markov could quite possibly be a core defender, Rance will be getting old, if we're lucky he plays past 30. Again if we're lucky and Grimes holds together then we might have a really good defense but it might also be the same some greats and a whole bunch of average. Vlastuin will either be a very experienced backman or a mid fielder. Batchelor will probably be gone, Houli retired, Yarran, who knows? McIntosh may have played 70 games by then, some kid like Menadue or C Ellis might be our main distributor of the ball.
It's not inconceivable we will still be playing Astbury in 3 years.