I tried to find information about this on the UESP, but without much success. There's been talk of Elves having excessively long lifespans, but I was wondering if there's any information on the respective lifespans of other races? It would be interesting to know if some of the characters from Oblivion or even Morrowind could technically still be alive in Skyrim.

There was one book in Morrowind about an acher that was narrated as a reply to some Altmer's mood after the death of his brother from "old age". I don't have the number handy, but it's in the mid-to-upper hundreds. Dunmer, as an effect of the curse that turned their skins, have shortened lifespans, but not as short as those of men. A few of the Telvanni wizards have expanded their lifespans into the thousands of years, Divayth Fyr in particular was something like 4000 years old, and still reasonably healthy, whereas Therana had definitely lost her mind in far less time, and Neloth needs ointment for his sore joints.

No clue about the lifespans of Kajiit, Argonians, or Orcs.