Gary Wang and Caroline Ellison did make a plea deal so that makes it seem like they are going to fully prosecute SBF. Any deal SBF makes will likely be to keep him from spending the rest of his life in prison.
It has been said elsewhere that he may be able to cooperate with forthcoming indictments of other players, such as CZ. So far though this is just speculation.
Also, it's fairly common for someone to initially plead "not guilty," even if they're planning to change their plea to "guilty" later. IIRC if you plead guilty, you can't change it later, so it's usually best to leave your options open.
That’s not what the article says. It says he will enter a plea later.
To enter a plea means to plead guilty or not guilty. All they are saying is that he hasn’t said either way yet.