Bitcoin is the most recognized cryptocurrency known by many people even they didn't even make a transaction or had a wallet in their life. It is decentralized and uses the blockchain technology so that controlled by a public system in which every user can be involved in. The software methodology among cryptocurrencies may change and even bitcoin system may be forked as software. Bitcoin has been forked and had no problem when it was forked.
The latest example was when there has been a fork which resulted with a new currency named bitcoin cash and everyone having bitcoin also had bitcoin cash at the same time which is free money. However bitcoin price is going up determined and if you have bitcoin there is nothing to worry about. But alt coins may be acting differently on graphs. Lately ETH is going up too while some altcoins go down. Some people may think that bitcoin price may be controlled by some group of people but i think it is not possible practically. A group of people can't effect price of bitcoin unless they have really serious amount of bitcoin. When you look at this page:
https://blockchain.info/en/stats
you can see how big trade volume is. When i looked it was nearly 50k BTC which is much more than 200 million dollars. And this amount belongs to just last 24 hours of transactions. Someone or a group of people really need to have relatively noticable amount of BTC in trade among this trade volume so that they can affect prices so much or maybe trade this amount in an exchange platform with a low volume to affect prices easily. So there is possibly no one who can change prices directly. I think this kind of an effect is much easier and possible to do using banknote currencies in several countries but not with BTC.
I also need to mention that the reason of hard fork which caused bitcoin cash is that bitcoin transactions are slow and they thought bitcoin cash would be a solution for that. I think bitcoin is not an ideal currency. It has advantage of being the first and most recognised so this is the reason it is so high valued today and may be it will continue for a long time. But if cryptocurrency related society has a common decision that another unit is much better for many reasons, than it can replace the popularity of bitcoin. This is possible when conditions allow. I see BTC mostly as an investment way rather than a payment method because there are some popular altcoins which allow you to make transaction in a short time. I think it's better to send money using another coin (ie. LTC) so the receiver gets it much earlier than using BTC for sending money.
