this thread on the CBS website is kind of interesting.
The OP noticed a lot of things that had been brought up here (like Mel's mom and the professor not at the funeral, the strange funeral, etc). She looked at them as 'hints' that Jim is in a sort of out of body experience. She thought that when Jim looked in all the rooms and then entered the scene before his funeral, that it was a look into a possible future that may not be.
They don't have numbered posts on that board, but the last post on page one has an interesting possibility - that as Jim gets back enough of his memories, he can go back and open the door to his hospital room and go back into his own body. Still kind of messy, but better than life with a corpse.
They also make some interesting points - like there are reports that the actor playing Sam is only appearing in 6 episodes and that "Jim" aka David Conrad is reportedly signed for next season. None of that makes sense if "Sam" is going to be the 'new' DH and Jim is gone for good once the viewers have made the 'transition' to Sam.
Maybe?
And, if this is not the plan, there is still time for the show to be re-written this way and they could pretend it was always supposed to turn out like this.
Sorry, I don't agree.
That OP is mixing Hollywood show business (and it is called show
business) with the storyline.
Mel's mom is Academy Award nominee, Anne Archer. She doesn't do bit parts or extra work. In order to have her on the show, they would have had to give her several lines & airtime, and pay her the big bucks she probably gets being Mel's mom.
The professor, Jay Mohr, is the
star of his own show. He's no longer under contract for
Ghost Whisperer. He doesn't ever have to appear on this series ever again. Also, he wouldn't be an extra either, they'd have to give him lines & pay him.
Both scenes would take up airtime, on an already weakly written episode.
Both, Archer & Mohr, are working on other projects or series (according to the IMDb.) Maybe they just couldn't be there for filming.
We really don't know if Sam is appearing in ONLY 6 more episodes. He's only listed that way in the IMDb.com.
A few weeks ago, for the show
True Blood, many of us noticed actor, Stephen Moyer, was only listed for 9 episodes, whereas everyone else was listed for 12. Moyer is the second lead on the show, (according to opening credits,) but his storyline was that he disappears for a while, so we weren't sure if he was coming back.
It could have been that who ever submits the info for him to the IMDb forgot, goofed, was late or the show just didn't want to give away what was going to happen.
In a few of the articles the producers wrote, they keep saying how they want to show us the magic of Melinda & Jim falling in love "from the beginning." I think they could have just conked him on the head & he got amnesia, but this is a series about ghosts, so I think they felt the need to kill him off instead.
At least, as someone else wrote, they got rid of those other story lines that weren't working, about Mel's father and the evil ghosts coming after Melinda. It seems to me, this is the theme this season: having Mel & Jim fall in love again.
Glad they showed David Conrad instead of that other actor. 
It's like we already know that they don't have their first date will Feb., because of the that website with the advance description of episodes. So I could just tune out & back in, in Feb & see the "first date." Lame. 
If anything, since I was the one who came up with the coma idea that was totally wrong, 
