Looks like we're getting close on this one. According to Guillem Balague, who's on Sky Sports talking about Spanish football a lot, the David-de-Gea-for-Keylor-Navas-plus-cash transfer has been agreed, along the following lines:
Navas accepts. De Gea deal done!! €40m all-in. £29m. Manchester United happy - near record for player with 1 year left
— Guillem Balague (@GuillemBalague) August 31, 2015
Presumably United would be happier if De Gea was staying, but hey ho, that was never likely. Now we just wait for official confirmation, pictures with shirts, then (from De Gea, at least), interviews full of praise for Alex Ferguson and platitudes for Louis van Gaal. Won't that be nice.
From the other point of view, with both Keylor Navas and Sergio Romero at the club, United fans are going to have to adjust to having not one but two goalkeepers who wear short sleeves. And as everybody knows, it is impossible to trust a goalkeeper that wears short sleeves. Worrying times ahead.