More worlds are always welcome, but I feel like there's so much needed content SP's can add, specially considering they can bring new gameplay features, that I'd rather have them.
Of course, if you ask me I'd rather have a new world rather than Moschino or MFPS, but if EA comes up with a good SP concept, I'm all up for it. There's so much they could do, like Wedding Stuff, Rock n Roll Stuff (including 90's clothes, piercings, bands and a rock radio station), Elder Stuff, and, I don't want to be a dreamer, but a "Fast Lane Stuff" including cars. Maybe even a Circus stuff pack.
I'd rather have worlds be included in EPs and GPs.
