If you were forced to upgrade and got a family share everything plan, wouldn't the WiFi tether be included?
I use "WiFi Hotspot & USB Tether Pro" by SVTP on my GN without root. It works perfect but at the time I got it I think it cost $10. Not sure if it cost anything now or how much. I plan on getting the S4 within the next month so I am hoping it will work on it.
Ok just looked it up on Google Play online and it is $14.99! But they have a lite version you can try for free to see if it works on your phone.
I use the same software on my GNEX and it kicks A$$. Paid $9 for it, too. Well worth it. Put it on my friend's S3 and it doesn't work. Tried it on 2 different S3s and no go. I'd be willing to bet it won't work right out of the box on the S4 either. That's going to be the one HUGE downside to upgrading to the S4. We used one of her lines for the VZW upgrade on the S4 and I will get to keep my unlimited data.