The PKK, Turkey, Russia, and Assad are all on the same page regarding the endpoint and always have been. Namely, that the PKK will be folded back into the regime. The only question, which is now entirely irrelevant given the US withdrawal, were the terms for the YPG.
Right now, Russia and Turkey are playing a "Good cop, Bad cop" routine with the PKK and the US. It's a strange dance, but nothing has changed: it's a two-pronged pressure campaign, aimed partially at the US but mostly directly at the PKK.
The Turks hope that by talking loudly and manoeuvring forces, they can compel the US, which is getting out anyway, to pressure the YPG out of the #Manbij, as @KyleWOrton and I wrote in March: capx.co/americas-syria… 
On top of this, they hope to scare the YPG enough to formally dissolve itself back into the regime. Russia is the other side of this foil, using Turkey to threaten the PKK unless it drops its demands and unconditionally dissolves.
Lavrov's converse threat against the PKK today: "We approach Ankara's plans to conduct additional counterterrorism activities in Eastern Syria from the standpoint of eradicating the terrorist remnants in Syria and reestablishing Syrian sovereignty & territorial integrity."
It should also be clear to any observer that the US has never had a stake in the survival of Ocalan's political project, so they're not really a relevant party. Their only concern was force protection and attacking Islamic State in the ERV.
Will Turkey attack #Manbij and invade Northern Syria? It's possible. They're certainly crazy enough to do it. But at this stage, there is little rationale to such an operation when every party's end goal is to dissolve the YPG into the broader regime structure.
In a better world, Turkey would ignore Russia and just do what it felt it needed to do. Unfortunately, like every other power involved, they continue to take Russia far too seriously trtworld.com/opinion/is-rus…
Turkey is engaging Russia as a factor in its approach towards the PKK. Which will end badly. Ideally they pull an Afrin, if only to make Russia look stupid. dailysabah.com/diplomacy/2018…
Not that anything Erdogan says should be taken seriously, but here's my little hypocrisy: he's now pretty explicitly saying that this entire thing is a game to get the YPG to transfer its areas to the regime axis reuters.com/article/us-mid…
Lavrov in October: "The main threat to Syria’s territorial integrity comes from the eastern bank of the Euphrates, where independent and autonomous entities are being created under US control."
It should be pointed out that for all the machinations of these actors, the only one both prepared & powerful enough to conquer vast areas East of Euphrates and hold them following a US withdrawal is the Islamic State.
