Obviously the Skyrim province has been there since Arena. I'm not claiming I discovered it just things I have noticed on my playthrough since skyrim has been announced.
In the dark brotherhood quest where you have to kill all other members. The ghost of Ruffio (your first victim) is (When your cursor is over him) named as ''Dovakihn''
In the quest in Shivering Isles expansion pack ''Symbols of office'' your clone is also called ''Dovakihn''
Some NPC's when asked about Rumours they speak of ''War in the North'' and ''corrupt Nords''.
The Skyrim logo is present on the Morrowind GOTY edition box art.
Also in Morrowinds in game start screen.
Spolier*
In Oblivions final cut scene Martin breaks the amulet of kings. Which is filled with Dragon Blood and the dragon of Akatosh emerges. Could the dragons returning be due to the smashing of the amulet?
Post any other things you may have noticed in the comments thanks :foodndrink: