1. It's reasonable to assume beast races live as long as men. It's impossible to visually identify a Khajiit or Argonian as being elderly, but we've seen in TES IV an Argonian having an advlt daughter. Note that the life span of men is also vague. We can only safely conclude the life span of men from the reigns of emperors. Uriel Septim VII is exceptional in that he has managed to occupy a span of over 80 years in the timeline, but whether this is due to his impisonment in Oblivion is not clear. No one knows how much longer he could have lived, as he was murdered. Many emperors are murdered, I dare say a third, so their reigns don't truly indicate the full life span of men. The only other indicator is M'aiq the Liar. In Morrowind he is level 5, in Oblivion he is level 40, which corroborates he is one in the same, and has done extensive travel in 5 years. Skyrim's M'aiq alludes to both his father and grandfather. Since there is a 201 year span between Oblivion and Skyrim, we'd need to know how many generations of M'aiq there are. The implication is there is more than 2 generations between both M'aiq. We also lack the information of how long it takes a Khajiit or Argonian to reach the age of reproduction. We know mer become mentally ready at the same time as men, from The Real Barenziah. The beast races may or may not be ready sooner than men.
2. I'm assuming that by "rising up" you mean becoming a national-political group that the rest of Tamriel recognizes and deals with as a society.
Orcs were just a type of monster in Arena and Daggerfall, it was Morrowind they became playable. As the games go on, Orcs are turning out to be the more noble of the races. Orsinium wishes to be its own province, separate from High Rock. This gives hope in how much we can interact with those rare but sapient beings in future TES games.
Imga seem like they're supposed to be... how to put this... that sort of race that when you look at it, you have the same expression you had when you saw Gungans in Star Wars. I see Imga more as an atmospheric amusemant the elves kept around rather than as a distinct people. They only emulate the Aldmeri, whom they readily view as their superiors. Read their description again, Imga do their best to make fun of men. The Aldmeri Dominion, and other such mer supremacists, must find that behavior entertaining. Imga just aren't their own people.
Sloads no doubt would be enemies, they have the most necromancy out of any race, and that says alot when Altmer have produced powerful necromancers. Dealing with a Sload NPC would be like dealing with a daedra NPC, someone incredibly intelligent, deadly, and no reservations about ruining your well-being. As Sloads live on Thras, which is near Summerset, we would only see them if we have a game centered on Summerset.
Lilmothiit probably were just a developer suggestion, the only text that mentions them does so with their disappearance in the same passage. The account of Lilmothiit we see is an arm-chair account compiled by informants with no direct record of Lilmothiit, but only second-hand oral history over a 1000-year period. If they resemble Khajiit, are nomadic like Khajiit, then maybe they were Khajiit.
Kothringi have a bit more lore than Lilmothit. They're supposed to be the only men native to Tamriel, exclusive to Argonia, and yet they got wiped out. Call me crazy, but I think the arm-chair lore may have misidentified the Kothringi. Consider that very little is still known about Argonians, other than implications they ingest Hist sap to become so reptilian (thus begs the question, "What does an Argonian really look like?"). The last Kothringi were thought to exist roughly 1500 years before the reign of Uriel Septim VII, when the literature was authored. Maybe Kothringi were just a proto-Argonian group that absorbed into the Argonians we know today.
The monster sub-category of the Daggerfall bestiary provides many clues. Look at the Giant and Harpy, you can learn their languages to pacify them. Giants are obvious, you see them in TES V and they *are* passive to an extent. Harpies? Well, if you presume a Harpy can walk upright on two legs, it could very well be a Hagraven, a couple of which in TES V do speak. Imps, afaik, never were passive or spoke in TES IV, so that's likely a retcon. Spriggans were only hostile in Bloodmoon and TES IV, but there are certain NPCs in Skyrim that do happen to be Spriggans, though they do have every intention of killing you after a certain condition is met. Dragonlings, Nymphs, and Centaurs have yet to reappear in a TES game. In Arena there are Lizardmen, who are very distinct from Argonians, but nothing more is seen of them. We have several instances of goblins that continue to remain violent despite their basic tribalism. Falmer function in tribal units, but are so eroded from the people their ancestors were that they fall into the same category as goblins. All the above taken into consideration, there's a distinct line between a sapient creature and one that's willing to function in a larger society, especially with outsiders.
Another race still known to exist but never seen is the Maormer. Their king, Orgnum, tried to invade Summerset, but his fleet was destroyed. There's no indication that Orgnum has been replaced as king of the Maormer, so the kingdom of Pyandonea still exists in quiet isolation. It also makes Orgnum for a very powerful person, not unlike Divayth Fyr. Moarmer loathe Altmer, so it might benefit the Empire to form an alliance with Pyandonea to defeat the Aldmeri Dominion. The possiblity of seeing Maormer in any satisfactory capacity rests solely with a TES game taking place on the Summerset Isles.
» Sat Jun 02, 2012 2:02 pm 
, i hope we see the imga one day, and these maormer i have never even heard of, ive always wanted to see another of nirns continents....but tbh i think it will be akavari because tamriel has had a bit of history with them.
