Well, if you look at the
Interactive Live Map of Syria you'll see that the Turks & Rebels working in concert have ground there way through ISIS at Dabiq, and are now working their way south through the YPG (Kurds). The Kurds can't stand up to Turk armor, and aren't getting any help from foreign actors, so they'll likely get swept aside pretty quickly. After that it's going to be direct Turk/Rebels on Russia/Syrian Gov't ground combat for the first time.
Shit's likely to get really interesting once Turk Leopards & F15s start blowing the crap out of whatever's left of the Syrian conventional forces. What will the Russians do once there's no Syrian military left to help protect their naval and air bases to the southwest? The Russians consider being denied warm water ports an existential threat. They can't rely on Black Sea ports, given that their enemy here, the Turks, already control the straits.
Maybe Erdogan will negotiate a deal with the Russians and just wants to start from a position of strength? I fail to see how he benefits from antagonizing the Russians, and I fail to see how the Russians benefit from shedding blood and treasure for Assad when in actuality they don't give a fuck about him personally - they just want bases. Maybe the Russians would be willing to turn on Assad and let the Turks gobble up part of the country in exchange for more secure basing under Turkish occupied Syria.