Are you mostly streaming games? If not I would wait for the more powerful K1 model.

If just android gaming keep your TN7 and pick up a controller if needed. I won a Shield from NVIDIA and sold it after playing around with it a few weeks. Its a great device, but for the most part, touch screen android games are a lot better on the TN7's bigger screen. I'd pick the TN7 for movies, music, etc. as well. Stylus support is a real bonus for me.
 
There are a few Shield exclusive games, so keep that in mind. Also nvidia's cloud gaming beta is free for the time being, if your wireless is fast enough and you live close enough to their servers. I tried it and it works perfectly. 
 
I'd skip the current Shield and wait for the K1 versiom or Tablet. Use your TN7 in the meantime. Just my opinion ;)

That's been my thinking as well... a friend gave me his Galaxy Note 2, so I've been using that instead of carting around both my old phone and my TN7, so my TN7 doesn't see much action except as a gaming device. My plan is to hold on to it until the K1 Shield is released, sell the tablet, and get the Shield. I have a perfectly good phone now for playing touchscreen-based games, and I'm sick of the finicky nature of my Moga Pro, so I'd much rather have something where everything needed for gaming is fully integrated. I'm also bummed that Console Mode hasn't been added to the TN7... I primarily leave it hooked up to my TV for playing games, and having to get up and fiddle with the touchscreen all the time is a genuine pain, so I'd rather have a device that is 100% for gaming, not just gaming-focused with other features. I'm also hoping they fit a 6" screen in the new Shield since I'd find it aggravating to have a handheld system with a screen smaller than my phone.