This is BTC hashrate:
From June to March it has gone up 4 times, but.....it has also gone 2.5 since then, unlike ETH.
So, what's the normal conclusion?
That is a far shorter time span ETH miners have managed to bring the hash rate closer to a point where it makes little sense to mine, this due to the availability of miners.
In BTC case, it was never a problem of having cheap electricity and mining not being profitable, and this is the reason we're having continuous growth as more and more ASICs are being produced and sold.
If indeed your assumption of ASICs taking over from GPUs in ETH mining would be real we would have seen a spike in the hashrate, right? Which is not there!!!!!
There might never be a significant spike in bitcoin's mining hash rate. Such efforts have the potential to be cancelled out by shifts in bitcoin's difficulty mining algorithm, which could reduce the cost effectiveness of deploying a significant rise in hash power. The type of spike you're looking for could also suggest a significant spike in ASIC manufacturing quantities, which is unlikely.
That entire chart you posted resembles a significant spike in btc mining power in my eyes. (Example: the spike above september 2018.)
Especially when factoring in decline of demand for nvidia GPUs and GPUs in general.