I don't think that for long term it is possible for more than 3 cryptocurrencies to last... and I will explain why.
Back in the 90's, there was a similar situation. The internet was blowing up, and people were buying .com website stocks like crazy. Just throwing their money at it because "there's no way I can lose money, the internet is the future". Everybody and their grandma was investing or creating websites. They all had crazy ideas on how to reinvent the way people do things. However, it all crashed... People eventually realized that these websites aren't working even though it was new. They realized that not everything that is new is good. Did the internet blow up? Yes. But many people invested long term and lost.
This relates so much to cryptocurrency. Everyone is saying to buy all these altcoins like stellar lumens, golem, bytecoin, Siacoin, and they all say the same thing. They look at the price and see it rising fast and claim "this will be the currency of the future".
I have a question for those people. How many purchases have you made with your altcoins? Probably none. Most people are buying up altcoins just for the investment without actually looking at how it's used. Altcions aren't used to purchase stuff. It is a currency that people only value due to the hype. The "currency" isn't even a currency for most of these altcoins. It's all hype. It's all people believing they are about to get in on a get-rich-quick method, when in reality it's all hype.
There are a few altcoins that will last. The top altcoins have a very good chance at lasting, but these random small coins will not. Ethereum, Litecoin, Ripple, Monero, Dash, ZCash, are a few. Eventually people will either switch to a few cryptos or the whole cryptocurrency market will never take off. There may be only Ethereum one day. We don't know. What I do know for sure is that people will look back on these hundreds of altcoins all claiming to be the "future of currency" and see how foolish it was to think that there could be 100 different cryptos.
Crypto has a huge future. Like the internet, Crypto will blow up. However, non-functioning coins will fail just like the many websites believing that they could revolutionalize the world during the 90's internet phase. The strong will get stronger, the weak will die.
Enjoy the altcoin hype while you can. I admit it is a great way to get money. I made money off of small altcoins blowing up too, but I am not planning on keeping them long term.
There is no such thing as an easy way to get rich quick.
PSA: DON"T LOOK AT RANDOM ALTCOINS AS A LONG TERM INVESTMENT. THEY ARE GOOD FOR DAY TRADING BUT THERE CAN ONLY BE A FEW IN THE END. ETHEREUM AND BITCOIN