In crypto land, anything's possible. All it takes if for a developer (or a group of developers) to being working on the project to make it a reality sometime in the future. Considering that competing projects already have a non-custodial mixer, I think that doing the same for Bitcoin should be a no-brainer. I've recently discovered a wallet called "Wasabi" with built-in mixing features. It might work exactly the same as TumbleBit, enabling privacy for those who need it the most. Samourai's wallet has the "Whirlpool" privacy feature that's similar to Wasabi's privacy mechanism. The more non-custodial mixers Bitcoin has, the more options people will have for achieving true privacy on the Blockchain. Non-custodial mixers are so much better than third-party mixers as you control the keys. But governments may not be happy with such solution. They might end up cracking down the industry in order to prevent people from obfuscating transactions on the Bitcoin blockchain.
Nonetheless, I wouldn't worry about TumbleBit's abandoned status since its code is open source. Anyone can revive the project in the future if there's enough interest in doing so. With Taproot closer to activation, we might not need a separate solution for achieving privacy on the Bitcoin blockchain. Transactions will be private by default via the use of Schnorr Signatures (someone correct me if I'm wrong). Expect to see governments react in a negative way towards Bitcoin as a result of the network upgrade. After all, they want to keep track of every transaction made on the Blockchain. Schnorr Signatures makes it harder for governments to achieve the task, making Bitcoin a high priority threat to the existence of central banks worldwide. No matter what happens in the future, Bitcoin will be here to stay. Just my opinion