Even if they're able to take Ankara, it is a large stretch to think that would mean Turkey is out of the picture. I don't see Greece holding any territory east of a few cities in Asia at all; the Turkish nationalist movement was better motivated, better armed, and better led. The West itself is not going to support Greece against a burgeoning insurgent movement - their unwillingness to manage the sandbox of states bolstered by WW1 was something that precisely led to WW2. The ethnic cleansing of Turks that is inevitably to follow - believe me, it will happen; pre-WW2 nationalism was a nasty thing, based on the idea of cuius regio, eius religio; just look at the Jugoslav wars to see the modern equivalent - is not going to make Turks happy at all; and a country like Greece is in no shape (fiscally, military wise) to take on the Turkish nationalist movement that will inevitably develop rapidly after the war bar some act of God.
Frankly, what fantasy led Greece to think they could actually conquer Turkey I can barely fathom. The great lesson of Balkan Wars + World War I was that a state cannot just 'handle' a foreign (nationalized) population - it's precisely why states have fractured more than they have enlarged since the modern era. Turkey was populated by millions upon millions of settled people, whose population was twice that of Greece's and which defined itself by a common identity. The subcontinent literally had depth equivalent to the entire Balkans, and Turkey was - is - too big for anyone to conquer.