Trump is about to open a mega can of whoop ass on WSJ and FOX News/Murdoch
Media has a lot of leeway when it comes to publishing stories like this so Trump will need to prove malice, which is really hard to do.
But at the same time, how low did the WSJ have to lower their standards to publish an article about a letter they do not have, and cannot prove its authenticity? If Trump can show the only reason to publish a story so weak in corroboration was to slander him he may have a chance at winning this. On the other hand, he is a political figure and the courts have been lenient as far as media taking shots at public figures.
My guess is Trump wants another settlement so he can declare victory and the WSJ may want to avoid a drawn out legal care and the discovery that goes with it. Trump will ask for sources, something the WSJ cannot provide.