I think Nyquist is fine. I think he may have physically peaked but he has a lot of room to grow mentally so I don't think an 80 point season is out of the question when it all comes together.
With that being said, I don't think he should be paired with Zetterberg. Zetterberg likes to rag the puck and hang on to it forever. Nyquist is good when he can exploit his quickness (acceleration/shiftiness not necessarily speed) and I don't think he can use it when Zetterberg is slowing the game down like he likes to do. I think Nyquist would be better suited to play with Datsyuk because Pav's has the ability to play a few different types of offensive games. He works well holding the puck, he can work a give-and-go with an intelligent player(which I think Nyquist is), and he can also work off the rush.
I obviously don't want to break Tatar and Datsyuk up because that has been working very well but I don't think Nyquist works as well with Zetterberg now that we know what Gus is capable of on his own.