Is it possible that the Count of Skingard from Elder Scrolls 4 Oblivion, Janus Hassildor is alive and maybe well during the events of Skyrim?

It is possible that he would survive 200 years, but what do you think is his fate? Could be be Elder Scrolls 6's version of Neloth? That would be cool.

I wonder. Maybe we could see him in TES online?

There is no significant lore of Skingrad after the events of the Oblivion Crisis. No evidence of it being raided by bandits like other cities in Cyrodiil during the time either. He may be very much alive.

And I wouldn't mind at all as he was pretty much the coolest count in all of Cyrodiil.

Doubtful that will take place in Era 2, while he was in the 4th era. He was also only a vampire for about 50 years before we met him

He may be still "alive" but there is nothing in Skyrim to say one way or another. Nobody knows for sure what effect the Great War may have had on Skingrad (if any). You never know, he may show up in TES VI (if there is one).