I look at it like this. If there are members of our current roster that are going to be core members of the team moving forward, it would be beneficial to have playoff experience. If we are in the hunt for a playoff spot, that probably means that Arenado, Gray, and Contreras had seasons similar to their career average. I know two of those guys said they want to stay, but if there was some significant interest in their services on one of the top contending teams, I'm sure that interest would extend into the offseason, so I wouldn't sell.
Now, my definition of being in the hunt means that we are comfortably in the playoffs if the season ended on July 31st. If we are waiting on a 12 game win streak to get us to leapfrog 3 teams in the wildcard chase, that is not "in the hunt" by my book and the calculus changes to trying to trade Arenado, Fedde, and Helsley.
Our future is more important than a low chance possibility of a playoff push this year, and the more assets we can get from others minor league systems while we try to rebuild ours shortens our window of mediocrity.