They will not replace fiat. There are many reasons.
But they will become the backbone of financial structure.
As far as regulation, it's nonsensical for the most part. First it's decentralized all over the world. It is peer regulated. Nearly every possible application of existing laws is for reasons that cryptos are immune to. The point of conversion is from fiat to crypto where regulation needs apply again. The other case is when cryptos are used in exchange for goods and services under the purview of a government - up until that time they are not no matter what lies Coin Center and know-it-all officials claim.
Consider this, once you have cryptos in a peer regulated system being used for liquidity of funds the government no longer needs to spend time and resources on them since they're immutable and essentially 51% attack impossible. That's ONE reason they aren't in the tax & regulation jurisdiction. (although illegally right now people claim they are)
maybe not replace fiat but they can lvie together side by side with any fiat currency just look at japan they have both their local currency and bitcoin living together with the same importance
i think yes altcoin need to be regulated if you want real adoption, otherwise many shop will simply not accept it,a nd it's the reason why amazon int he first palce is not accepting it
There's a fair chance that fiat will become digital, but replacement is another ball game of a privatized world most likely.
Altcoins don't need regulation. They are going to fizzle at least 4x faster than mobile app investments. I actually have a fun idea for them. What if when you go to buy coffee you can pay with something that has wallets for all your altcoin stuff. You basically set up rules of agreement. I want Doge coin to pay no more than 2x what it's worth and I want to use it first, up until X dollar amount; after that I want X coin to ____. And the coffee shop can accept/deny any that it wants to as well, while also setting a general rule for conversion rate. For example I'm the coffee shop and I want 3x what the Doge coin value is or I'm not taking it, you get a message that says "insufficient funds: no transaction/use litecoin" or whatever... That way you can literally use altcoin for those willing to play games with them. Just a thought to have liquid assets.
As far as tokens go we need PEER REGULATION on them. For example I'm Bancor 2.0 and don't want to fudge up an ICO. I submit tokens pre-sale to multiple websites for review of the smart contracts. Those website can rank and review the code. I imagine some website would be public ranking, and others by pros, etc... if I don't do this no one will join my ICO because I'm sleazy and afraid to show my smart contract. Aside from that people have access to a gazillion times more information that they did in the 1920's so if they make bad investments now it's no one else's problems. There's always a sad story. We let people walk into casino's with their mortgages in hand, why not a chance at a legit business?