Depends how quickly you need a NAS (and any of the potential new features the upgraded one will have).
Can't find any specs online, but it'll probably get a bump from 256MB to 512MB in memory and will go from USB2 to USB3. Some of the other DS213 models now have 2 network ports and it will probably get a processor speed bump.
If any of those are of use to you, then I'd wait.