like wikipedia when you hover over a link:

it will show a preview of the post's contents (without formatting and with a 250-character limit; will get cut off after 250 characters. if post is shorter than 250 chars, it will just show the full thing).
i.e.:

it could even show the OP's information. what do you think?

Due to the Forums being made on DjangoBB, there mayn't be a high chance it gets implemented on this iteration of the Forums — Although cheddargirl had mentioned that there is high certainty of a wipe and archive.
However I'm not a person who works on genuine coding so take me with a grain of salt that's the size of shrek's house.
Semi-Support

While this would be cool, the forums are run on DjangoBB, which is pretty outdated from what I've heard (it may not even have support anymore).
If the Scratch Team ever moves the forums to a new architecture (or whatever terminology you use), this could be added, but for right now, I don't think it will be added.

Why not just click on the post link to see what it's about?