Does it make sense to be more aggressive in predicting by giving the user a second level from which to choose? For example, if he types 'b', then it could offer to type 'black' or 'black hole'.
On the iPad, for example, if I type 'f', I get shown 'for', then if I accept, I always see 'example' and 'instance'.
Suspect "sometimes, but rarely," because choosing "hole" after "black" is pretty cheap--you need your expected savings from potentially saving that choice to exceed the cost of bumping your worst option from the list. It's more likely to be practical when you can offer lots of choices rather than the typical three on mobile, though (bumping a 10th choice is cheaper than bumping a 3rd choice).
Separately, predefined phrases/templates can be really practical for things related to care, food, saying hi and bye, etc. That's a special case--user likely cares more about getting it done efficiently than choosing the exact wording they want each time.
On the iPad, for example, if I type 'f', I get shown 'for', then if I accept, I always see 'example' and 'instance'.