As living and existing culture they're out - even if there's one half-amnesiac corprused survivor and maybe a handful of not insane ghosts lingering around.

To be more accurate : in a RP taking place in the third/forth era (near Morrowind an Oblivion's timeline) the dwemers have dissapeared for something like 3000 years. A dwemer character in such a setting would be about the same as having a spartan soldier (from Sparta, antique greece, 500 BC) showing up as an important character in a WWII movie like 'save private Ryan'....

Lifespan wise, I'd go for the usual elven ones, minimum of something like 20 years old, maximum at something like 600 living in good conditions and having acces to the best medical care.

From hat few names are mentionned in Morrowind's book and the dwemer ruin's names, they tend toward unpronceable (B'Tuanc Mzanch or Arknthand aren't exactly what I'd call smoothly flowing names...)