If I were to root my new S5 does that mean I would never be able to do a OTA upgrade without deleting the root?
I don't have an S5 so I can't give you a guaranteed answer, but if it's similar to the S3 then the answer is - it depends. It depends on the root method and what it changed, as well as what you've done with root privileges. For example, if you've frozen or deleted any built-in apps (bloatware or system apps) there's a high likelihood that the OTA will fail to install.
If you used a simple root method like Towelroot and haven't mucked with the system then the OTA will probably work, but there's also a good possibility that the phone will no longer be rooted when it's done. YMMV.
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