I don't think this is just talk anymore. I think this is going to happen, and it'll happen within the next 48 hours.
Consider the words.

“Is the duty of protecting NATO borders left to terror groups? We can protect our own borders,” said Turkish Prime Minister Binali Yildirim, according to Turkey’s state-run Anadolu news agency. President Recep Tayyip Erdogan accused the United States of betraying an ally and threatened to attack Kurdish “terror nests” along the border.
“Those who stabbed us in the back and appear to be our allies ... cannot prevent it,” said Erdogan, according to an Anadolu report.
...
In his remarks, as reported by Anadolu, Erdogan said he did not “even think of calling U.S. President Donald Trump to discuss Syria,” adding that “as he long as he does not turn to me, I do not turn to him.”

That's pretty harsh.

Turkish troops and tanks near the Syrian border are making final plans to attack the US military’s Kurdish partners inside northern Syria as tensions between Ankara and Washington near unprecedented levels.

The Afrin canton is a measured choice, because it is likely that the U.S. doesn't have any troops there.
It'll still be a bitter fight, and the Turkish-backed jihadists likely will not win without direct help from Turkey.
However, where it gets interesting is Manbij, because we do have troops there, and Turkey has already said they want the YPG out of Manbij. It required both U.S. and Syrian forces putting their troops in between Kurdish and Turkish forces to prevent a conflict around Manbij before.
An assault on Manbij would bring NATO forces into conflict, which has never happened before. The implications are completely unknown.

Meanwhile, ToP still hasn't noticed this.