If I am not mistaken isnt there a huge age gap between all TES titles, there was between Morrowind and Oblivion and now in Skyrim its two hundred years and I guess its a direct sequel because there is a V at the end of it.
Oblivion was 5-6 years after Morrowind. I don't know much about Arena and Daggerfall, but I think all of the games took place in the 3rd Era.
Skyrim is not a direct sequel because of the V, that doesn't even make any sense, why would it be because of a simple "V'? That's just 5 in Roman. It's not a DIRECT sequel at all, just a chronological one.