Perhaps it depends upon how you define crossover.
Will Nick meet up with Rick? Probably not.
Could he walk the walk? It seems that he does.

So... since you are so definite that there will be no crossover, please tell, how are you defining crossover?

 

In the comics, the whisperers, came out of no-where.
There is nothing saying that a similar group couldn't start on this side of the country, maybe use sign language, maybe whisper.
Whatever, means they use to communicate, the story line could be completely different.