There is a reason I quoted Frank Herber's Dune in the title of this post. Sure, Erdogan arrived to St. Petersburg and held meeting with Putin. Many general statements were made but nothing changed and it shouldn't. Here is a decent piece of analysis from TASS news agency:
Fact is, I don't know where did this "triangle" idea come from? Ever Eurasianism-mongering Alexander Dugin went as far as to claim that fates of nations and even of civilizations were being decided in St. Petersburg and that Erdogan-Putin meeting was "historic". Well, it certainly was not and for a simple reason--Turkey needs Russia for her bargaining with EU and US. True, after the coup attempt and seeing its proxies being obliterated by SAA and Russian Air-Space Forces in Syria, and with economic noose around her neck as a result of reckless downing of Russian SU-24, Turkey needs Russia, but only so far. Yes, there is a very lucrative deal in the offering--Turkish Stream plus some other economic projects, but Turkey still remains a NATO member and firmly in the grasp, however slightly weakened, of Atlantist structures and she will remain there for a foreseeable future.
Once all this lofty rhetoric about Russians and Turks bound to be friends and even allies dissipates, the reality remains unchanged--no alliances of any kind are possible between Russia and Turkey. Milking each-other for economic and geopolitical benefits--that is a totally different matter and this is precisely what happened in St. Petersburg. Russia needs a leverage of Turkish Stream to both bypass Ukraine (or whatever it became now) and to improve her position vis-a-vis Europe and this has been, all things considered, achieved. Yes, this is, actually, huge but hardly historic let alone implying any possible alliances or "triangles". After all, Iran is not exactly Russia's friend either and the status of Caspian Sea is still being discussed. Plus Iran is a player in the region and does not always like Russian influence there. For now, what happened in St.Petersburg is mostly economic discussion with hard questions of war in Syria left to be discussed later. I would say--good movement, or, rather, step in the right direction but no more than that. But there are plans within plans and we may only guess what they are, since the play with Turkey (and Iran) is merely an episode, however important. My guess is that, in the end, the big play is for Europe, the real one, and the only goal here is to save her from herself and those who see her as merely a marketplace. Call it a hunch but, in the end, Russia, like no other, has an experience of saving Europe and paying the price with others taking credit. How it will be done? I wish I did know what Putin does;-)