Next Ethereum? How is that even possible to predict? With the way people keeps joining Ethereum community, with all the developments done by the team so far, with the fact eth 2.0 will be launched soon, I think there is nothing like any project replacing Ethereum for now.
I think the true question is "what is better than ethereum" because we can't know if something will "replace" it but the uniris blockchain will be for sure better than etherum 2.0 anyway and that's why I mentioned it just before, you should look on it, it's a great deal.