FTP? You mean the not-encrypted during transport and login FTP?
Yea, no way that'll happen

The data is encrypted in 1Password but we generally want encrypted transports as well. Dropbox and iCloud both use SSL between your device and the service.
SFTP probably won't work either but for different reasons. Hopefully I can explain the reasoning.
At the moment the most common format 1Password uses across all devices is called AgileKeychain, it's something we designed way back when we were making 1Password 3. (2008-ish) And this format has a separate file for each item in the database. So, if you have 100 items, you have approximately 105 or so files in the data format. FTP doesn't inform us really which files have changed since the last attempt at syncing, this leaves us in a tricky situation that usually means we have to download the entire set of files to check against the existing data. This would be extremely slow.
The new format we are pushing to get into all the applications going forward is called CloudKeychain but it's a slow process since we have 4 major platforms that are all different. Mac and iOS both mostly support it and as does Windows. But Android does not. So, we can't make it the default for that reason. Hopefully soon though.
With CloudKeychain we have a lot less files as each item is assigned to 1 of around 15 band files. This means there are often far less than 20 items that need to be downloaded, until you factor in attachments, those are all separate files as well and scale linearly with each attachment added.
So, things like WebDav and SFTP might be more likely once we switch to CloudKeychain for all users, but I can't promise anything... we have to support the services that the most people will end up using. We have to test, support and maintain each of the sync services we add to the application. That's a lot of work and each time we add more we have fewer people who are experts in all areas of sync and that makes supporting customers even more difficult. Plus, when it comes to WebDav and SFTP you have to worry about individual implementations of it that may cause bugs and issues that are out of your control but users expect you to support and fix. The big nice thing about Dropbox and similar types of services is that they mostly work consistently and we don't have to worry about those details.
I'm not saying it won't happen, but I'm also not saying it will. We'll see how it all pans out in the end but I hope the details above show that there are a lot of details that come into play with how we choose and decide to support various sync solutions. It's not as easy as just adding support for it.