So, if this calculation is valid. It means the price after the halving will at least doubled from this current price and it's make sense. So, i'm sure it's the buts time to buy bitcoins because the hashrate will doubled right after the halving held. But it will only happen when the demands is still the same just right now. If people are leaving and no investors are interest with bitcoin the price maybe less.
Hashrates have never been (or at least, as far as I know) a factor in judging possible market pumps and dumps. Market price fluctuates and changes because of the supply and demand of BTC, and how willing is the market to accept a certain supply for a certain price.