On the subject of macguffins we don't want to see. I hope they don't use something from the previous films, like the Ark has been stolen by someone. The only reason I say that is that although I enjoyed TFA immensely, it was a very simple plot that harked back to the original films in its story and aesthetic look and it makes me wonder if Disney would do a similar thing with Indy and recycle old ideas and stories and play it safe.
In the back of my mind I'd always thought Disney would reboot Indy and do an origins style story featuring Indy and Belloq in some early adventure. But I hope 5 is an all new macguffin and supporting characters.