As an American, I think that describing the UK or Ireland as having "a lack of language barriers" to be hopelessly naive.
"The United States and Great Britain are two countries separated by a common language." -- George Bernard Shaw
I wouldn't be a bit surprised if Germany had a higher percentage of people who are fluent in American English than the UK or Ireland. :)
Anyway, according to the EU, Ireland speaks Irish Gaelic, and when the UK leaves, there will no longer be any officially-English-speaking countries in the EU. That's going to have some interesting repercussions! (Unless Scotland manages to wrangle a way to stay when the rest of the UK leaves. Which I know they desperately want to do.)
But yeah, Brexit could be a real boon for Ireland. Possibly enough to make up for the fact that their current biggest trading partner is planning to leave the union. I'd certainly be looking at Dublin as a strong alternative to London. If I were the Irish government, I'd be out pitching "we're not leaving!" to all sorts of companies!