Browsers have been supporting Javascript for decades. This legacy language is the fuel for interactive websites, and some of which are not even maintained, yet they are popular. Ditching Javascript for the cost of users won't turn out good for browser vendors.
There can be other alternatives like WebAssembly, but it is not going to replace Javascript very soon. Though you can write code in different languages, and convert them to Javascript, using some transpilers, ultimately it comes to the point that the Javascript realm is second to none.