From everything I've seen and read, I just don't think Nolan is that kind of guy, I feel pretty confident we won't see the Joker again, I feel like Nolan would think it somehow disrespectful or not honoring Heath's memory to just recast Joker for the next movie.
Agreed. Simply put, the real world forced his hand. This isn't any role. It's not the very much alive Katie Holmes doing a passable Rachel Dawes. It was the defining role of an actor who died tragically before his work hit the screen. It is a role which accolades and awards are being piled on - not only as an acknowledgment of his fine work - but as a eulogy of sorts.
Who wants to walk into that minefield? There are now so many pitfalls and potential negatives in the form of unfavorable press, comparisons and hard feelings, that I would imagine the cons far outweigh the pros. No one wants to have their film enter the cinemaplex with that kind of (potentially) negative baggage. Not when there are other stories to tell and other villains to tell it with.