After watching episode 10 on Sunday I find it very interesting that Bran told that ghost story right after what we saw in episode 9.
Nah, he intentionally wrote Tyrion, Arya, Jon Snow and Danaerys to be very likeable and they're still around.
Put up or shut up, George!
(just kidding - I'd hate to see any of those four characters killed off...and would probably stop watching the series if either Tyrion or Arya was killed.)
As a writer, Martin seems to be doing a masterful job, with the small portion of the series I've read and/or watched, in selecting who dies. He's keeping villians around long enough to make them truly threatening and make you really want to see them dead, but killing them off just frequently enough to give us the catharsis we need. As for the heroes, the ones he's killed were either necessary to push the plot forward (Ned Stark) or ancillary enough (Caetlyn, Robb), so that their deaths, while sad, still left the readers with more central heroes to cheer on. After all, the deaths of Ned, Caetlyn, and Robb just make you want to see Arya put a sword through some Lannisters that much more...
Spoilers (sort of...but not really if you've been paying attention to Arya's character arc)
Speaking of Arya, who do you most want to see her assassinate one day?
My list, in rank order:
1) Cersei
2) Joffrey (even though I doubt it will happen...can't see him living that long)
3) Tywin
After watching episode 10 on Sunday I find it very interesting that Bran told that ghost story right after what we saw in episode 9.