When is this to come into effect and will it be active restrospectively? Just wondering if I should mix my coins today before it goes into effect.
Discussion
Laws are generally not retroactive. But here's the thing: if you mix your coins now and send them to an exchange in 5 years, they might freeze them and ask annoying questions - because that's what that law forces them to do. That's already a risk today.
In other words: the duty to do compliance stuff is not retroactive. But the compliance people can look as far back in history as they see fit.
Use trustless swaps (with liquid) before going to a centralized exchange to offramp or deposit with lightning. Take a USDT loan with your btc as collateral (hodlhodl) and use that to offramp. And do it only if you really need to make use of the fiat surveillance network.
You're still assuming presumption of innocence exists. It doesn't for AML/KYC. You're presumed guilty if they can't fully trace your coins.
I doubt they will ever be able to implement and enforce this kind of totalitarian detailed complex massive surveillance and chain analysis and interrogation processes but we’ll see what 🤡-world comes up with next. 🍿 Worst case we’ll exit the EU. 
If by "we" you mean bitcoiners, then perhaps yes. But if you mean the Dutch then you should realize that this proposal could have been vetoed by the Dutch government. Instead they probably lobbied FOR it.
If by "they" you mean the government, they don't need to. They'll just tell the companies that it's up to them to do it, and if they don't, they'll get a fine of a percentage of their yearly turnover. That's what the EU does.
In which case, should you mix your coins now I may presume you incurred in terrorism, trafficking, money-laundering at any point in the future.
I mean, the solution can't be "don't mix your coins", but it also can't be "be as noisy about it as possible".
The trick is to resist the injustice, while finding ways to stay alive.