You can be unlocked and get otas. Not sure if an app like ota root keeper would work to keep root. But since this is a nexus, I'm sure root will be available quickly, after the ota, if you want it. You might (not 100% sure) be able to have root and still get the update, as long as your recovery is stock. Might break the root though.
EDIT: As long as the recovery is stock, not CWM or TWRP, you can be rooted and the update will install. But it WILL break root. You will still be unlocked though. And getting root back is easy, since this is a nexus.
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