If Disney Infinity had released a year earlier, then we definitely would have seen playsets for Oz, Frankenweenie and likely Wreck-It Ralph. It's all about the timing. Of course, had the game released even earlier than that then we would have most likely gotten a John Carter playset as well. ;P
If actual code exists in the game for these characters (and they didn't stop at just concept drawings like these) then I could see them being released as standalone figures down the road... the yellow brick road, that is.