In theory all the Z9's are already running and have been counted in the hashrate. That's what everyone says, that they have been running for months.
They have been. Everyone purchasing them are about to get what Bitmain has had running on their shelves while they replaces the Z9 "mini" on those shelves with Z9 "beast." However, they only turn on enough of the Z9 "beast" to equal pretty much the same hash rate they had before taking Z9 "mini" off the shelves to ship to those purchasing them. THEN [Once at least 50% of their Z9 "mini's" are sold, they begin slowly turning on more Z9 "beast" but not too many... They don't want to discourage noobs from purchasing their Z9 "mini."
So why are the DEVs getting their panties in a bunch? When Batch 1 is released it shouldn't raise the hashrate at all correct? It's batches after that we have to worry about.
Mere speculation... Mainly based off your first comment about ASIC's "already" being on the network. Cause they ARE on the network. You'll see if and/or when forks are implemented and watch the hash rate plummet.
Also, if they change the algo, I don't think it will take long for BitMain to release a new miner. They seem to have building miners for GPU only coins down, and it they don't Baikal will.
This is just to do something to try to keep ASIC's from pushing out GPU's all together. This may be good for 6 months. If ZEN and other Equihash coins were to do this every 6 months, it could discourage BITMAIN and other private ASIC manufacturers from wanting to try this again. R&D on another chip would be about 6 months for BITMAIN.
Have a look at PROG PoW. https://www.youtube.com/watch?v=P6B-ZCyP6K8&t