At that time, Polkadot is very promising, but now it seems that the coin cannot rise up significantly. And Moreover, now there is Matic that is also considered as the next of Ethereum.
So, actually, which one is the next?
Will there be always new crypto that is considered as the next of Ethereum? Or it is just a claim?

Okay, just live that trust and confidence, and let see what will happen 1 year from now. Sure mean SURE but in this crypto market, I can't see anything like that, not unless if it has proven already like Bitcoin and ETH, and you tried to compare Polkadot to known ETH, I would be saying that I hope you were right.
I am not sure about this. Probably there will be other coins that also claim or consider as the next ETH again.
This is like an old cycle like what happen to Neo at that time and many more coins. Just different era will be different coins again
A lot are aiming for the next ethereum, why not create their own path in crypto market? Also, better develop their platform first like attract many projects as they can. Because if the developers are happy with the network, word of mouth is a very powerful tool. So for me, don't chase to be the next ethereum, instead find ways how to serve better the crypto community, because you can make your own name without following someone's trail.