Skar actually was resurrected in the Fourth Era during the Oblivion Crisis (the time The Elder Scrolls IV: Oblivion takes place) when Daedra were invading the city. It's described in the text The Fall of Ald'ruhn:

Michael Kirkbride wrote:

From the annals of the Crisis:



"The armies of Oblivion destroy Ald’ruhn, ancestral home of House Redoran, even though ancient rituals were used to awaken the dread emperor crab and the whole city literally rose up to fight the invaders. With their warrior House decimated, the dunmer of Vvardenfell fall back as daedra move towards a siege of Ghost Gate. Prayers to Vivec and the Nerevarine go unanswered."

Merry Christmas, V, and holiday cheer to everyone!

-MK (Michael Kirkbride)

REMEMBER REDORAN. NEVER FORGET.

The resurrected Skar wasn't able to save Ald'ruhn, but it certainly helped defend the city. When the Red Year occurred five years later, Ald'ruhn was completely destroyed by the lava of Red Mountain, and its unknown what happened to Skar.