No one can give you a good anwser on this.  Just to many variables are still out there unanswered and having is still a long ways out in mining terms.

We don't know what gen miners will be out then, and what the efficiency will be.  Also someone might mine and sell to a "free" or lower priced electricity person on new gear now.  So mining and selling is a valid ROI.  I like to ROI before selling, but with having coming.. you never know.

We just need variables that we cannot possibly even speculate with accuracy.