It has bothered me since "Jughead," when the additional survivors of the flaming arrow attack failed to "meet at the creek," that we do not know who or how many actually survived. But I believe this was done in part so that Rose and Bernard would not need to be accounted for in each episode; after all, they are only guest stars, and several main stars (Daniel, Desmond) have barely received any screen time this season.
Here's what I think, based on Darlton's 2/5/09 podcast where they confirmed that at least Rose, Bernard, and Vincent are still alive, as well as my own observation of the time flashes: Rose, Bernard, Vincent, and any other survivors (which I imagine is three, maximum) are in 2008. They experienced the initial time flashes with everyone else, and were obviously present in 1954 when the flaming arrow attack occurred. At that point, they "headed for the creek" and waited for anyone else to show. The next two time flashes occurred, and suddenly they were in 2008, shortly after the arrival of Flight 316 (as exhibited by the broken-down camp and outrigger canoe with the Ajira water bottle). We know that Sawyer and his crew then took one of the canoes and were shot at by as-yet unnamed assailants; suddenly, the next flash occurred and saved their butts. But that flash -- which took them back to 1988 -- did not happen for the Bernard crew. Somehow, the Flight 316 survivors interfered with this.
I'm guessing that before the season's end, our survivors in 2008 will see the flash that put our 815 survivors in their time for that brief period. Someone -- Sun, Frank, Ben, Locke -- will be in the right place at the right time and find Rose, Bernard, the dog, and whomever else. Through some kind of interference or poorly-explained sci-fi reason, this will cause them to stay in 2008 when the next flash occurs.
There are a few reasons I think this is the case: 1. I find it hard to believe that any additional Flight 815 survivors made it to 1974 and have been there for the past three years without being seen or mentioned; 2. I doubt that they were "dropped off" in any of the other time periods, due to a simple lack of practicality in the story; and 3. The writers love their end-of-season cleanups. Usually this means killing all the Others or blowing up the freighter, but in this case such a move would consolidate all the minor characters (Rose, Bernard, Frank, Ilana, Bram, Vincent, Caesar if he's not dead) into one place and time and make it easy to explain their whereabouts and actions in one blanket statement.
One final note... I hope there are at LEAST one or two redshirt survivors with them. To think that everyone else would have been killed except a dog and a slightly overweight couple in their fifties is a bit of a stretch. But then, it is LOST.