I would like to remind everyone that when Google first started offering itself as a search engine, everyone was CERTAIN that AltaVista was the best search engine out there and nobody would ever be able to top them.
We can see how well that assertion worked out. Younger tech users are sitting there saying, "who?"
Which is precisely my point. Companies ebb and flow. Some will rocket to market dominance, only to have a meteoric fall later. The question should not be if, but when, and who will replace it. It's only a matter of time.
Do you mean Google as a company or Google as a search engine?
In the first case, if you are referring to Google as a company, it would be difficult to imagine a new company, even if it is blockchain-based replacing it in the future.
That's because the Google company has grown so big, developed too many products, and has even diversified its company into several profitable verticals that it will be difficult to replace it. Can a new company compete with it, in the future? It is possible. Facebook, for example, is competing well with google in the online advertising space even though it is a much newer company. However, they can only compete with Google when it comes to online advertising. On it's other verticals, Google still seems to be dominating.
So, in this respect, even if a new blockchain-based company emerges, it might only be strong enough to compete with Google on some aspects of its business, but perhaps not in its entire business. At least, not in the immediate future.
If it's the second case, there are already a few blockchain-based search engines that are trying to take some market share away from the Google search engine. One example is Presearch. It's a blockchain-based search engine that rewards community members with tokens for using, contributing to, and promoting the platform. They're goal is to be an open and community-driven search engine alternative to Google.
However, whether Presearch will grow big enough to replace Google is still up in the air. We have to consider that blockchain technologies are still in the early phases of adoption. In order for Presearch (or another similar blockchain-based search engine) to compete with and replace the Google search engine, cryptocurrencies and blockchain technologies must be adopted by the public, first. Once that happens, it might be possible to replace Google. After all, why would you keep on using a search engine that is profiting from your data and not sharing the profits with you, when there is a blockchain-based alternative that is willing to reward you with tokens that you can exchange for money in the real world.