1. of course the price of altcoin will also increase very high, because more investors will invest and use cryptocurrency;
2. there will be no significant changes if Bitcoin is accepted by the country, because Bitcoin is already very popular, so Bitcoin and altcoin prices will definitely continue to increase every time, even if Bitcoin is accepted or not by the country;
3. because many companies are starting to use cryptocurrency (Bitcoin and altcoin) for their projects in the future;
4. it depends on you, if you want to invest for the long term, then you better to hold.
1. Not all altcoins but only the best ones because they are the ones which investors HODL and invest more. Many of us are going to be happy if more people will also use their cryptos regularly and not just idling them to earn a profit.
2. I think there is. Once Bitcoin is accepted, alts can too. Our crypto experience won't be completed without an altcoin because BTC lacks some features which can only be found in Bitcoin. BTC might be popular already but I think there are still lots of countries or people who are not yet involved with it. They can help the price to rise evenly.
3. I'm not really sure about it but it can also depend on what type of company it is.
4. That is the objective of long-term investing. That is, one should HODL long enough.