Looking at the current trends, it is difficult to believe that the US authorities are going to tolerate Bitcoin as a decentralized currency, and Bitcoin mixers are further down the line. To put it bluntly, the government will never get comfortable to the level of anonymity provided by Bitcoin. Sooner or later, they are going to act against this. The mandatory KYC verification for exchanges is just the tip of the iceberg. In future, KYC will be mandatory everywhere, including wallets and crypto-related forums including Bitcointalk.
I don't know how many of the mixers have the required licenses and permits to operate. I doubt that the majority don't have any. Even those with the licenses may face hostile action from the government in the long term. Illegal mixers will be treated the same way as the authorities are treating the dark markets (such as Aplha Bay and Silk Road).
Exactly. That's what I've thought in the first place. As soon as governments realize that Bitcoin is unstoppable, they'll take their efforts in trying to destroy it at all costs. The situation becomes worse for mixers/tumblers, and even privacy-oriented solutions for Bitcoin (such as CoinJoin-enabled wallets like Wasabi and Samourai). Their main excuse would be that they're trying to fight money laundering and other illegal activities. But the truth is that, most criminals use Fiat for their nefarious actions instead of cryptocurrencies like Bitcoin and Ethereum. The main reason is that cryptocurrencies are extremely volatile, whereas Fiat is not. This makes it a terrible solution for wrongdoers (not to mention that most cryptocurrencies are transparent by design too) as a means to "launder" money.
Despite these facts, we cannot deny that sooner or later, governments will take actions against centralized mixing services. They've already began taking action with centralized exchanges where KYC is a must in order to trade cryptocurrencies within the mainstream world. We've seen the case with Shapeshift where it was once an "Instant Exchange" that allowed people to exchange cryptocurrencies in an anonymous manner. On the other hand, the US' IRS agency has been against every US citizen using Coinbase.
It would be unfortunate if Bitcoin wallets end this way. If this happens, then the only means to send/receive Bitcoin would be within the "Core" Wallet which serves as a node to secure the Blockchain. Hopefully, developers would come up with a solution that would allow people to send/receive Bitcoin, and even obfuscate transactions without the intervention of governments worldwide (by making government's efforts harder to achieve over time).
Nonetheless, what we need is decentralized alternatives to current mixing services. Luckily, this is already in the works with TumbleBit, CashShuffle (Bitcoin Cash), and even the Dandelion Protocol. Which means that, privacy might be obtained with ease after all. Just my opinion