Whispers about the Dwemer also echo throughout Skyrim. Like the Snow Elf the Dwemer are also believed to be in Morrowind. Although the mysterious disappearance of the Dwemer is thoroughly woven into Elder Scrolls law (such that bringing them back would be a canon-strainingly big deal), it hasn't been explored thus far.
The Dwemer pulled their disappearing act during the War of the First Council's Battle of Red Mountain. Lord Kagrenac constructed Kagrenac's Tools to harness the powers of the Heart of Lorkhan, also known as the Stone of Red Tower. The disappearance of the entire Dwemer race is believed to have followed an attempt to use the tools and the heart to make the Dwemer a race of immortals.
The fingerprints left around Skyrim indicating the Dwemer disappearance mystery could be a fascinating narrative arc, and potentially have far reaching implications on the Elder Scrolls universe. Since they were snubbed in Skyrim and Dawnguard, the next piece of DLC would be the perfect opportunity to explore the race further.