Autocorrect for specific people and the language they use I don't think this option exists, but doesn't hurt to ask. And it would be amazing if Apple could implement this option in case it doesn't exist.

I have people that I correspond that speak different languages. It would simply amazing if my devices and apps (Mail, Messages, Skype, etc) would recognize who I am writing to and remember what autocorrect language I had set up for them.

That way, it would always autocorrect the appropriate language without me having to switch it. (On the actual Mac, switching the languages is not even an easy step).

I hope there is some solution in the meantime other than just turning autocorrect off.. :)
When editing text, right click and choose "Show Spelling and Grammar":



Select Automatic by Language:



This works for me, I use two languages (English and Italian).

Edit: This is for Spelling and Grammar, the setting for autocorrect is in Keyboard->Text:


You'll also have to add the languages you will use in the Languge &amp; Region panel of System Preferences.