We have the same problem about Tweet cards caching.
The same URL links to an updated content, including Tweet Cards Metas, but tweets that refers to that URL do not reflect changes of the landing page… An the Card in the time line shows old content, even if we tested the URL in the preview tool…
I’v tried @episod trick who suggests to add get parameter following the URL… And it work.
But indeed, I guess there should be a tool somewhere, in dev.twitter.com, for instance, to refresh cached URL, for us not to have to add get parameters each time we tweet the same URLs with new meta content…
There is a similar issue in Facebook about sharing link in the status. Facebook provide somewhere a way to refresh cached content…