This topic is interesting but you are thinking it the wrong way.
There is no "next bitcoin" or next superstar. Stop searching for this.
There will be other ways to make money with 10.000% or even more, but it won't be next bitcoin. It may be totally unrelated
I don't know any other digital asset. Maybe Amazon gift cards or such?
That's a fair point. I think the reason for that is that Bitcoin is so much more than some digital asset. Sure, it can be used to gain profit, but it can also be used to store value (preserve rather than profit) in a bank-free form, to get a feeling of a truly free market, so own money that is not controlled by any government or other entity, to possess something valuable that cannot be faked or to perform financial transactions without revealing the identity. And these are just some options that came to my mind.
A new superstar asset might be good in terms of profit but have no other important features or have those which are very different from those Bitcoin has.
But what's going to be the next big profitable thing - I have no idea.