Einstein was writing in German. He knew French, but his cousin had to translate into English for him.

I also agree that English language is very important in science.

First, we need some language to cluster research. Scientists are mostly not polyglots; few can write well more that in 2 languages. Since native language is different for all, there should be one in common for majority.

Which language to choose? If we calculate speakers, the major 3 languages will be Chinese, English and Spanish. Then goes Russian, French, German.

Now let us look how science has been developed. Indeed, a lot of research during the last century has been written in English, German and Russian. But German and Russian remained  closed clusters with fewer users than English.

Scientific research must speak a single language. The English or any other language. But this would not be possible to decide "at the table" see the case of Esperanto. The United States of America by about half of the last century are the dominant nation as regards scientific research and beyond. Therefore, all researchers had to read works written mainly in English and to be readed by a large number of researchers had to publish on USA magazines in English of course. Although the most widely spoken language in the world is Chinese.

Do you think that in next decades Chinese may become main language of science?

I'm pretty sure English as the language used regard to scientific publications will no longer be changed. Certainly, like all languages it will also evolve it and maybe in the 1st or second century of the years 3000 will not be the most English which we use now, but it will not be the Chinese and none of the other languages spoken today. Moreover, even the Chinese researchers regard to scientific publications are using English.

I am very glad that you say that,  maybe Chinese is a nice and interesting language,  but I wouldn't like to learn it when I will be 50 or 60.