There's very little information on this move as of the time I posted this article, but here it is.
The Cubs won't be going with three catchers anymore, at least according to this tweet from Yahoo Sports' Jeff Passan:
I have literally no other information on this move at this time. No other national nor local Chicago writers have tweeted about it, there's no information from the Seattle side, and no word on who the Cubs will receive in return. I'd guess that minor leaguers are involved in the return, but that's strictly a guess.