tl;dr, It is too late to start mining with an S7, you are too late to the party/train/whatever. Party's over, the train has left the station. Bitmain S7 is a junk anyway, lots of S7 are dying, they didn't last a year unlike the S3's. All the biggies are replacing the S7 with the 16nm new gen miners. Don't be a bag-holder of last gen miners.
It is not necessary to late, so many variables I never say to late. First we have to look at electricity price... for some very cheap others not so much. The OP at .09.... is not cheap but more "normal" range. So it's a little harder right now.
But not knowing what having will do to value, or hashrate at that point we cannot give good speculation on a lot. It is just hard to say. I bought one of the last of the previous gen S5+ (was right before S7) and I did pretty well on it..... so cant say late can never make profit. It was also one of my favorite miners and it was late in that generation.
