As for using bitcoin illegally, I don't think it's a wise idea. If you don't need government legitimacy you can also use shitcoin or any asset as currency as long as you reach an agreement between seller and buyer, not just bitcoin.
What people need and aim for is bitcoin to become a legal currency, not the idea of using it illegally.
Governments wouldn't want to miss the huge taxation benefits that comes with legalizing Bitcoin, right? It's possible most of the world's countries will open their arms to the cryptocurrency just to "get a piece of the pie". I'm starting to think that even countries that once turned their backs against BTC (like China and Russia), will eventually change their minds about it. I'd say Bitcoin has already won. Whenever it can save you or not, depends on how you use it. Just focus on "hodling" it more than spending it, for complete peace of mind.
Bitcoin's only been around with us 15 years. I'm certain it will survive way beyond the very last halving if it continues to grow as usual. Decentralization is key towards the long-term preservation of the cryptocurrency. Who knows how much a Bitcoin will be worth in the future?