This is actually a topic I've addressed before.
A reminder that even without the UK, more people in Europe will speak English than any other single language by a wide margin. 42% vs 30% for German, and 25% for French.
Consider Sweden, Finland, Denmark, and the Netherlands. Each has their own home language, different from the home language of the others, but all have high proficiency in English. Any move to get rid of English as a language will result in these countries getting irritated, at minimum.
There are, in fact, more English speakers than German speakers in every EU country except Austria and Germany, where the language is Official and Native, and, more English speakers than French in every country except France, Luxembourg, and Belgium, where the language is either Official or Native. The remaining 22 countries all speak more English. You can drop that number to 20 if you count both Italian and Spanish as separate languages for this purpose, and 17 if you count Russian, and 16 if you also count Polish. Even at these levels (English vs German, French, Italian, Spanish, Polish, and Russian) there are still 16 countries that speak English more VS 11 that speak one of these languages more.
In short; even without the UK, and even without Ireland and Malta, who are staying in the UK, and where English is official, English is the #1 most used language in Europe, and will remain so for the time being.