Call me a canonist or a purist or close minded or whatever it was a dumb idea to begin with.
I like the idea of Vader being the one to take out Ahsoka... but there's probably too much money in Ahsoka staying alive for her to be taken out like that.
If we're guessing her fate, I'll guess she was on Alderaan with Bail when it exploded... that's the real reason that Obi-Wan was able to feel it's destruction from so far away.
Although the Ahsoka dying on Alderaan is a good one, I doubt that's the reason Obi-Wan could feel it. Millions of voices crying out in terror and being suddenly silenced would create a great disturbance in the Force.