Thread makes no sense   

What in the world could make BTC untreadeable for cash? And how in that kind of scenario would it be tradeable for anything else at all? How would then anybody want to or be able to still buy them on say purse.io (so you can spend them)?

This thread makes no sense...

Is it about the market price going straight to $0? That's only possible if there's nobody that would want to pay a penny just to own a record in the oldest blockchain.
Is it about some kind of law prohibiting fiat<->crypto exchanging? Then why would anyone accept it for goods or services at all? Are we assuming 100% of all humans on the entire planet would abide by this law and no black markets would emerge?
Is it about a hypothetical technological innovation/advancement that would be strictly better than Bitcoin in every possible way and not worse in any single way - something that would obsolete Bitcoin entirely and cause all miners to turn off their machines? Even then the old BTC would still retain some value as a collectible, even though it would require significant money to pay someone to run a miner and write a block.
Is it about a technological or environmental catastrophy that would break Bitcoin beyond any possible use? Global nuclear war? Massive worldwide neverending electromagnetic storm? Invention of a way to break into any computer from a sattelite and just delete all copies of the blockchain in existence?

Or is it about a scenario where you cannot trade BTC for cash because there's no cash other than BTC - that case would be epic win.

You need to be more specific with the doom and gloom visions so we can discuss reasonable outcomes or rather convince you it's just impossible to happen.

I have 3,000 hungarian forints in my wallet, right now. That's cash but I'm quite far from Hungary right now, and there's no place where I could exchange them to the local currency. So they're basically worthless, but as I'm planning to go back to Hungary in a few months, I'll keep them preciously. Same thing could happen to BTC. It could be worthless among the majority, but a minority will keep on believing in it, so it'll keep some value elsewhere, among other people.

The single most important improvement of bitcoin would be using it as a medium of exchange. I've been supporting sales with bitcoin and I myself have bought many goods like online games and hosting services with my bitcoins. However, each time I spend my btc buying something I get the feeling that it would rise and I'll be unable to make profit. Stability, with it deserved price (values same as the dollar's marketcap worldwide), is the position we must somehow enter. So we can use btc as cash.

i would exchange with other coins and the turn it into cash. if that would be possible

If BTC was to no longer be traded for cash, chances are i would either exchange it to something else that can be exchanged for cash (e.i. another altcoin or something) or I would go and buy whatever i can with the Bitcoin that I have, and get some good that can be sold at a later date, even if it is for a loss. At that point it would basically just be anything that I could still buy with bitcoin I would buy, and then I would see if the process could be repeated. if i could do that, then I would consider keeping up with he community, but if that process wasn't repeatable, then chances are i would stop and go on to something else.

Can you clarify this? If Bitcoin cannot be traded for fiat, it means that it has no value, right? If Bitcoin has no value then how can you spend it on Purse.io? I am a little confused about that.

Anyways, to answer your question, I would probably do what everyone else seems to be doing. Store it and wait for the price to rise again. If it doesn't seem to go up for a long time, I may just switch with by investing to some other Altcoin like Ethereum.

I understan your attempt but if bitcoin king of crypto doesnt exchange anymore to fiat i do believe all altcoins will be on the same boat, meaning they wont as well, or the price should get too big. I dont expect never bitcoin loose it support with fiat.

Do you think there will be an altcoin left once butcoin fall or doesnt have a price anymore. What will ETC or ETH supporters thinks when that happen. I bet they will all be scared that they may be next in line which will lose its value.

I really dont want to think about that for whatever reason but if it eventually happens, I am sure there will be another way to use the bitcoin in which we are all going to go for. But its going to be a great setback...