In general, I would always say that removing functionality, even if it is perceived as not widely used, without providing an alternative way to achieve the same thing is a retrograde step.
The Unanswered tab is a good feature. I do sometimes trawl back through the old questions to see if there's anything worth answering. That's not to say I use it all the time (or even very much at all), but I like the fact that it's there.
However, the way it's currently structured isn't great. You've got four tabs:
[my tags] [newest] [votes] [no answers]
So... what if I want to only see questions with no answers and also filtered by my tags? And possibly sort the results by votes? The above tabs don't help with that.
I would suggest a good replacement for the Unanswered page would be to add some filtering options on the main questions page (or possibly add a "Filtered" tab to the main questions page, which would provide the filtering options). The user could then specify exactly what he wants to see. It would be more flexible than the current Unanswered tab (although don't make it too flexible, or it just becomes too hard to use for an average user).
This idea would allow you to drop the Unanswered page without dropping any functionality; in fact, it would increase functionality.
As for the Review page that you want to put in its place on the page layout.... well, you do already have a link to it on the main page, when there is anything to review. But that's certainly not all the time, so when there isn't anything to review, what would happen to this new button?