I agree, the 50 limit is rubbish, and it says now we need to upgrade to have more than 50... Less is (costing) more, it seems. Come on Adobe, answer the question!
I apologize for the confusion on that message. Upgrading will NOT permit you to send more then 50 files in a single transaction. (There's an engineering request in to fix that dialog.)
If you want to send more than 50 files, you can zip them up into a single file and send them that way. (Note that zip files aren't previewable by the recipient. They need to be downloaded.)