Ignoring the prequels is a nice thought, but I think it's a pipe dream. Episode VII will be taking place in the future of Episode VI, where it's already been established that Yoda, Obi Wan Kenobi, and Anakin Skywalker have retained their personalities as Force spirits. We know that the original characters (Luke, Han, Leia, etc.) are going to be in Episode VII, so it stands to reason that we're going to see Ewan McGregor and Hayden Christensen (and CGI Yoda) or else the movie's going to have some explaining to do as to why their spirits just suddenly stopped appearing. Those of you who want Episode VII to ignore the prequels: have fun with that part of the movie.
Since I've never believed that Luke would have been able to recognize Hayden's face at the end of Return of the Jedi (which is a problem I've always had with inserting Hayden there), I think it would be hilarious if Episode VII had a running joke about it: whenever Luke sees Hayden, his reaction is like "who are you and why do you keep appearing to me??" Kind of like the guy spraying the kid with the hose in "Billy Madison." I suppose Luke wouldn't recognize Ewan McGregor either. And how weird is it for Obi Wan to change from McGregor to Guiness and then BACK to McGregor again? But it's going to happen, because the ghosts wouldn't arbitrarily stop appearing after Episode VI.
In all seriousness though, there's a bigger issue that the prequels created for this sequel trilogy. Instead of making the prequels as a standalone trilogy with some elements that connect them to episodes 4-6, George Lucas chose to make it so that all 6 episodes form one story focused on one guy (Anakin/Vader). Everybody distinguishes between the "Sequel Trilogy" and the "Original Trilogy" as though we have two separate and distinct trilogies, but that's really not what they are. They are one 6 part story (hexalogy??).
1-3 don't stand alone as a complete trilogy story. Revenge of the Sith is no more resolved at the end than The Empire Strikes Back. I understand three movies were released during a different generation from the other three, with many different cast members. And I distinguish between "trilogies" because I love 4-6 and hate 1-3. But from a story perspective, we don't have 2 trilogies.
The issue this creates is: the sequel trilogy has to take up different subject matter now, because Vader is dead. This would be fine if Abrams' movies were a separate standalone series in the same universe and they left the numbering system of "1-6" alone to be a saga about the rise and fall and redemption of Darth Vader, but he's not doing that. He's calling these "VII, VIII, IX, etc."
This means that Star Wars is about to start becoming a very lopsided saga, where one long saga about Darth Vader unfolds across six episodes, followed by a trilogy at the end about something different (but with some familiar faces included). This is going to make the sequel story feel "tacked on" to the larger story about Vader, but only because Abrams is joining the two together as part of the same number sequence.
The only way to remedy this and restore "balance" to the saga (pun intended) would be if J.J. Abrams purposefully gives his Episode IX a very unresolved ending, and doesn't wrap up the story/character arc that he begins in Episode VII until his Episode XII. But I don't think that's what's being planned (I'm sure Disney will eventually go all the way to XII, but I think they're planning on making VII-IX a complete story that can stand on its own, rather than having one singular subject that starts with VII and ends with XII; I may be wrong). Lucas changed the Star Wars format from trilogy to hexalogy; and Abrams is acknowledging this with his Episode numbering but then contradicting himself with his intention to make a "trilogy" anyway.