Very risky move. If you look at how protocol changes in other altcoins have been handled, where has always been a grace period of at least a couple of days. This gives all miners the time needed to update to a newer version.
What is going to happen if you don't get the majority of miners to adopt the new protocol in time?
That said, I've updated my miners (300+ cores) to the new protocol version. Lets hope that we get through this smooth.
I have a pool with 3000 miners that has migrated and the other major pool has too.
Solo mining already takes a week so only 10% of the solo miners will be effected because the rest would not have found anything anyway. If the difficulty adjusted as it should then these solo miners also wouldn't have gotten anything. I think it will be smooth as these things go.
That is not how this works. All solo miners with the old version of the miner can be seen together as one entity with a certain hash rate. It doesn't matter that some people are not getting any blocks, some will. And its not only miners who have to upgrade, also people who just use the software to make transactions.
This could be ugly:
The old miners will just make an 4x adjustment. They accept any blocks whether it be the ones generates with lower diff (4x increase) or higher diff (32x increase max).
The new miners reject blocks with lower diff (the ones with 4x adjustment), because these blocks don't match the new requirement. However they will produce blocks much slower than the old version of the miner, so many people using an older version of the software will make invalid transactions!
Thus: Any payments made with an older version of the client could get lost and someone falling for that could easily be scammed.