I too would love to see a little scene where the Doctor 10.5 and Rose are in the Parallel Universe, happily married under 10.5's "John Smith" alias, and nicely settled down in their new life together, looking to the future.
I just can't help thinking it would be lovely if 10.5 felt or sensed the regeneration of the Tenth Doctor, and he tells Rose, giving her total closure once and for all, so she can finally move on with her life, knowing that she's with "her Doctor".
I think that would probably be the perfect ending to Rose's story, because for me, personally, the way they finished her story in "Journey's End" wasn't right. It just didn't feel right. It felt too *forced*. So I think just one little scene, right at the end, where Rose just knows that the Doctor's regenerated, would be the best possible ending for her story. It would do the character of Rose justice.
And besides, it would be nice for Rose to re-appear just once more, right at the end of the Tenth Doctor's life, because if everyone re-appeared, just for a short cameo or flashback sequence, it would be paying tribute to the Doctor's truly great legacy, and it will be giving everybody a proper send-off before the dawn of a new era on the show.
Doctor 10.5 and Rose Smith, walking off into the sunset together.
Yeah. Perfect ending.