As the wikipedia isis page has not been updated at all (the high-ranking source of information for those who complain about the content of other users' posts), the incursion of Turkey into northern Iraq is certainly an event which will have important consequences in 2016.
With Kemal Ataturk's military victories at the start of the third decade of the 20th century the treaty of Sevres was never applied.
The 1923 treaty of Lausanne stipulated a provisional boundary in Iraq, with a final agreement to be signed later.
But the League of Nations ended up assigning the Mosul province, with its 600,000 inhabitants, to Iraq, and in 1926 Turkey reluctantly had to sign this agreement.
Turkey's President Suleyman Demirel, in 1995 (during operation steel, when 35,000 Turkish troops entered northern Iraq):
"The border is wrong. The Mosul Province was within the Ottoman Empire's territory. Had that place been a part of Turkey, none of the problems we are confronted with at the present time would have existed."
http://images.mentalfloss.com/sites/default/files/styles/insert_main_wide_image/public/ottoman_empire_territory_lost_copy_copy.jpg (Mosul province within the territory of the Ottoman Empire)
The Turks see the current situation in Iraq as a golden opportunity to regain their real estate.
Iran cannot enter Iraq with its troops, unless there is a clear provocation (some kind of attack on Samarra's Al-Askari mosque, as an example).
The most ominous aspect of the situation in the Middle East is, of course, the bizarre incursion of Saudi Arabia into Yemen (certainly things could have been done differently) which was a sure sign that more was to follow (the 34 nation coalition organized by Riyadh ready to fight isis in iraq).