My reason for disrecommending the S7 is exactly that. Even in ideal mining condition, such as 0.05$/kWh ~ and 2-4% diff increase from now on, no more 5% and such, no pool fee and no BTC price plummeting, the S7 will not ROI by halving, at which point any profit after that is dubious at best.
We do not know what will happen at halving. Prices could go up or yes many miners will have to stop. We cannot say with any certainty this far away.
One thing to keep in mind is the selling of the machines. Even if someone has higher electricity they can mine with it for quiet a while. S7 will still hold value at around having, they might have to sell to ROI. But with owning a newer miner the good thing is value is better. Look at SP20, S4 S5, Avalon 4.1 to show the trend of miner still having good value even though they are not the most current.