Yes, the new unlock will void your warranty for good because you're updated the iPhone's baseband to that of an iPad (no going back after that).
To upgrade to a future update would be iPhone suicide. The iPhone Dev-Team or whoever would have to figure out a way to unlock the iPad baseband again. So updating would be a big no-no, unless there is a solution.
For now, I suggest not upgrading and changing your baseband. Wait for a better way to get the unlock. But if you really need it then go for it. If you can wait, use another phone.