Thing is, I’d reckon Jedi survivors are a certainty. The Order is too widely spread and the Galaxy is very big. Even if in the wildest dreams of Palpatine, if Order 66 and the Inquisitors got 99% of them…there’d still be a few dozen of them left. And the Outer Rim is a very easy place to disappear…
But not in the way Ahsoka did. And I’m going to be brutally honest, but she should not have walked away from Vader, let alone fought him on semi-equal terms.
It seems to me that some Jedi must certainly have survived Order 66, but 1) a lot of them had already fallen in the war, and 2) the massacre of the rest was really well set up. So there would indeed be only a bunch of stragglers. Of those, I think most "fully trained" Jedi would be inclined to do the Right Thing, which means try to organise some kind of resistance during Palpy's early reign. At which point they get hunted down by Vader. That's the whole point of the Purge.
What remains, then? Some apprentices, who survived due to their Masters sacrificing themselves. The fact that they have fewer skills makes them less likely to become leading resistance leaders, which increases their chances of surviving. Maybe there are a few trained Jedi out there, but I think Vader's efforts would be directed at finding those, and that in the intervening two decades, they'd slowly be hunted down and killed.
In the old EU, the instances of some Jedi apprentices (basically "small fries") surviving were pretty credible, and since Force-sensitivity was assumed to run in the family, this then created a bunch of Force-sensitive children of said survivors, and those kids could later be trained and help rebuild the Jedi Order. Although he was a bit of a Gary Stu, Corran Horn's back-story made sense in that regard. The guy never even knew his grand-dad was a Jedi, and his own dad was never anything like fully trained (Nejaa having died when Valin/Hal was ten years old).
Conversely, I always thought it was somewhat implausible that Qu Rahn (from
Dark Forces), survived through 5 ABY. (Especially since it would make
zero difference to the plot if Jerec had caught up to Qu Rahn in 1 BBY, killing him then.) The difference being that Qu Rahn was -- exactly like you'd expect from a justice-loving Jedi -- heavily involved with the Rebel cause. So him staying off the radar is just not that believable, really.
So, yeah-- I think survivors would mostly be "small fries", like apprentices who slipped between the cracks and learned to keep their heads down (first out of sheer terror, being basically kids living through a nightmare, and later out of well-honed survival instincts). The bigger fish would be more likely to get caught, because unlike Yoda and Obi-Wan, they wouldn't adopt the (rather un-Jedi-like) approach that "just suffering through it" is the correct choice. Because they don't know about Luke and Leia, and all the reasons why Yoda and Obi-Wan believe that the children of the Chosen One are the galaxy's only real hope...
Does this forum have a 'reboot the Sequel trilogy' thread or something to that effect? This is probably faint praise, but I'm guessing most people here could probably come up with something better than whatever is now canon.
There have been some discussions about it, but generally spread around across various SW threads, I think.