Really, it is more of a plea (as published in WaPo):

Mr. President, please cut it out. Tweet to your heart’s content, but stop the wildly inappropriate attacks on the attorney general.

[…]

The attorney general is not — and cannot be — the president’s “hockey goalie,” as new White House Communications Director Anthony Scaramucci described Sessions’s job. In fact, the president isn’t even his client. To the contrary, the attorney general’s client is ultimately “We the People,” and his fidelity has to be not to the president but to the Constitution and other laws of the United States. Indeed, the attorney general’s job, at times, is to tell the president “no” because of the supervening demands of the law. When it comes to dealing with the nation’s top legal officer, you will do well to check your Twitter weapons at the Oval Office door.

[…]

Mr. President, for the sake of the country, and for your own legacy, please listen to the growing chorus of voices who want you to succeed — by being faithful to the oath of office you took on Jan. 20 and by upholding the traditions of a nation of laws, not of men.

I would not recommend anyone hold their breath.

I do think that of all the mistakes, blunders, and bizarre tweets the President has issued, his attacks on Sessions may be the one that gets the most traction because it is inside the GOP and Republican Senators in particular are not going to take kindly to it.  Plus, Sessions was a mainline politician who threw in with Trump early, helping him build credibility with certain segments of the party.  For Trump to come at him on loyalty of all things will be galling to some in the GOP.

If one is wondering why the former President of Baylor University’s views are salient on this topic, go here.