A question I'd ask is whether the "hole" in your lens lineup makes a difference to you. For me, there's no problem with just swapping to the 50mm and even forcing framing with that (zooming with feet) but obviously this can be troublesome and it is difficult to carry all of your lenses comfortably (and wearing a photo vest all the time is not for everybody).
If you find that you're able to get a lot of use out of just a two-lens combo and it's comfortable, you might stick with that (I would). If you're feeling you are missing shots or that it's too much stuff, you can try for the other lens. I would keep in mind, however, that it might just end up being another lens to add to the pile, because it doesn't replace a 70-200mm, or even the 50mm and 17-40mm, in my situation. For you, it might replace the wider lenses, and that 70-200mm might not be too much extra to carry around, or it might be left at home most of the time.