The risks of losing the fungibility of coins in the open blockchain in the future may differ from different points of view, depending on future development scenarios and on individual risk tolerance.
There are no associated risks as long as you use bitcoin peer-to-peer. Such risks only arise if third parties, which are prone to regulation, are the backbone of the ecosystem. I don't recognize any third party which, if shut down or regulated, would take the entire currency with it.
You do not live in a vacuum, but in real life. If necessary, you will be deanonymized not by the peer-to-peer payment passed through the mixer, but by the context of the payment. And using a mixer, you only attract additional attention to yourself, advertising that you are hiding something. You can deceive yourself as much as you like, but anonymity and privacy are a myth in the modern world.
Why would I want to advertise the fact of mixing my coins?
I don't argue you advertise such thing; I'm just saying that if someone tries to trace you on-chain, it's good for you to have them known you've used a mixer. That clarifies you are not the owner of all mixer's outputs, and that the history prior mixing is not important.
If you want to make an anonymous payment, it's much more reasonable to use a monero-type blockchain that was initially closed than to try to obfuscate the trail in a public ledger like bitcoin. Mixing in a mixer gives the illusion of privacy, which, like any self-deception, is sometimes much more dangerous than its complete absence.