Turkey may have just created a Russian-backed Kurdistan by shooting down the Russian jet. If the Kurds are willing to fight, the Russians might yet give them the nation they’ve been pushing for. A couple of billion dollars a year and state-of-the-art SAM’s in PKK hands would give the Turks endless headaches.
Russia help Kurds carve out a country, inclusive of Kurdish areas in Turkey. Sounds very reasonable, especially considering that the US has failed the Kurds. Blame it on Obama.
Turkey's main interest in Syria, other than Assad's ouster, is to make sure that the Kurds don't get too uppity, or else their fellows on the Turkish side of the border will start getting ideas. Since the Kurds are pretty much the only ones in the region other than Assad who are putting up a fight against ISIS, at the very least Turkey is allied with ISIS by proxy.