Rupert Murdoch will not live forever, and the 'Sun King' is considering his legacy to when he turns his eyes at Wall Street Journal. Rupert is very smart, and he will repeat what he did with the London Times - a few journalist will leave (especially those reporting from China), a few editor will resign or be kicked out, but overall the newspaper will remain the same as before. Except that it'll be a tabloid.
The real troubling aspect of a Murdoch takeover is this.Suppose a journalist reports a story that embarrass the Chinese government, and the Chinese government want the source of the story. Will you trust Rupert to protect the source?
As to any undertaking that Rupert Murdoch promise the Bancroft family, here is a little history lesson. News Corp is an Australian company until a few years ago. When it made the move to Delaware, Rupert made many promises to the Australia shareholders about corporate governance issues (as the rules are more lax in Delaware), and then promptly broke every single one of them.
When Rupert finally pass away there will be a 'mother of all inheritance' battle between the children of his first wife and his second wife (who is Chinese). There is a good chance that WSJ may ended up being owned by the Chinese government, now wouldn't that be swell..