FWIW wrote such a thing years ago but finally don't use it. The reason:
in case an abbrev is forgotten, rather store a new one easier the
remember than learning the old one.
The problem I have is that I forget that I have abbrevs defined in the
first place, for things I type. My problem is not (primarily) that I
forget exactly what a specific abbrev is. Abbrev suggestions would
simply remind me to use the ones I have. Like every habit that you try
to create, it takes time and effort. This feature would help me with
that, I think.