I just found that tweak today! (Changing some registy values myself)
Go to: Local Machine\System\Input
enter in the folder that corresponds your alnguage id (in my case is lang_0416 for Portuguese Brazilian)
add the string ".disable" in the end of the values of "Dictionary File" and "HTR Dictionary File" and restart your phone.
Next time you type something, you should not be bothered again with the prediction and auto correct.