If miners stop mining and buy coins directly, then it makes obtaining coins through mining cheaper. The two must cancel each other because the demand does not change. The supply is unaffected, so the price does not change.
Long term wise, the demand is rising every year, the supply is shrinking every year. People have much more fiat money than bitcoin, the fiat money inflow will not stop in the foreseeable future, price will rise forever and the mining cost roughly decided how fast it will rise
