Hi there!
Thanks for getting in touch! We do support imports from iCal URLs with iCal Importer, so files stored on Dropbox should work as long as the URL given is a direct link and publicly accessible. However, without testing your particular file(s) and setup, it’s difficult to make any guarantees. In this case, I’d encourage you to take advantage of our 30-day refund policy to test an import and see if it works as intended! Should you run into any issues along the way, we’d be glad to provide further support and troubleshooting.
I hope that helps! Thanks again for your interest, and let me know if you should have any other questions!