I agree that Ahsoka will most likely survive at least the initial execution of Order 66. However, something big is going to have to happen with her at some point. Why, for example, is she not even mentioned in Episode III? And where is she during the Galactic Civil War and the incessant chaos that's taken place since then?
This can be answered with simply, "where was anybody during the galactic civil war."
Like i mentioned before, there were jedi that survived order 66, and their was other jedi around during Episodes 4-6, but where were they during those episodes? Luke, Obi-wan, and Yoda were treated like they were the last of their kind, but there were other jedi, and those being trained to become jedi, but they were no where to be seen in the original movies... they didn't get even the softest mention.
The expanded universe is all about retcon, and inserting new events in the blank spots inbetween the old events (mostly the later)... episodes 4-6 were the beginning of the starwars universe and most of the characters that appeared before and after were barely even conceived at that point and were written into the timeline afterward
Ahsoka can easily end up the same... in the comics and novels they will tell us why she was not mentioned as she was somewhere else... They will tells us that she was working under another jedi knight towards the end of the war, and that when order 66 was handed down, that knight sacrificed himself to make sure Ahsoka escaped... they will then find something for her to do as she grows up. During the galactic civil war she was either in hiding, secretly training force sensitives, or maybe even helping rebels fight the empire in another part of the galaxy...
The events we are told in starwars have plenty of weeks and months of time between them... and they only tells what is going on in one part of the universe at a time... it takes no effort for a writer to place Ahsoka into the timeline and just tell us that she was involved in [insert never before mentioned event] on [insert planet] while [insert pre-existing event] was going on... hell they could say that she was in hiding, and then inbetween episodes 5 and 6, she finally came out of hiding took a shot at vader, lost a hand, got badly injured, and was unable to participate in fighting in episode 6; she would then join the new jedi order afterward and have all sorts of adventures that we previously never heard of... also she has a son and names him after Plo Koon... whatever floats the writer's boat