Right now we are in a very interesting time in the development of cryptocurrencies, while I believe in bitcoin we are still not sure if it is going to be the dominant cryptocurrency in the future, segwit was a step forward and it decreased the fees somehow, if the LN is really successful then bitcoin will be the dominant crypto for decades but if it fails then another crypto with superior technology will have the open door to try to take that place.
Yes. It's a very interesting time for cryptocurrencies indeed. Ever since SegWit was activated last year, Bitcoin has seen a sharp decline in fees, as well as increased user interest. Now that this has been achieved, it's possible to use the Lightning Network within Bitcoin. While LN has many benefits to help improve Bitcoin's scalability, it's not a perfect solution as some people say that it will make Bitcoin more centralized over time.
Perhaps, in the future, the Lightning Network would become successful enough to handle all the world's payments, while retaining decentralization which is the value proposition of any blockchain. If LN could remain decentralized, then there should be nothing stopping it from becoming used in the mainstream world. However, if all else fails, there's always the option of altcoins since they have already implemented certain upgrades for scalability (like Bitcoin Cash's 32MB block size).
In the end, it will be up to the people decide what's best for Bitcoin in the long term. Just my thoughts.
To tell you truth, bitcoin cannot be vanished or disappeared from the world. Bitcoin is so much adapted and used all over the world that no one can even think of leaving it. There is only one possibility is that we found a severe bug in the blockchain which may make all the bitcoins lost, but this again is no gonna happen.
Exactly. Bitcoin has grown strong over the years, which makes it practically impossible to become dead anytime soon. With the current amount of hashrate available on the network, as well as, the number of nodes distributed across the world, it would take a lot of effort and money to make Bitcoin disappear. However, if Bitcoin never scales to expand itself to a greater number of users worldwide, then it would be doomed as other cryptocurrencies with better technology will take the lead.
Only time will tell us what will happen once Bitcoin fails to scale in the mainstream world.