Here's a workaround to start syncing folders on Windows right now. It's a bit command line heavy, so you might need to set this up for your users. But I would much rather do this than use some other syncing solution and then have to migrate.

(1) Create a remote server git annex repository with the assistant on Linux or Mac.

(2) Install git on the Windows machine.

(3) Install git-annex for Windows on the Windows machine. Don't forget to run the installer as administrator.

(4) Run Git Bash from the system menu, and run these commands to clone your repository.

cat .ssh/ | ssh "cat >> ~/.ssh/authorized_keys"
git clone
cd annex
git annex init

(5) Create a script that will trigger a full sync

echo '
git annex sync
git annex get *
git annex add .
git annex sync
git annex copy * --to origin  
' >
chmod +x

(6) Copy the "Git Bash" shortcut from your windows menu to your desktop, and change the link target to:

C:\Program Files\Git\bin\sh.exe" --login -i "annex/"

Now ask your users to run this shortcut before and after they change files. You can also put it into the "autostart" folder to sync at boot.