The news still keeps on coming. According to Sakurai, SSB4 will not have a SSE as an Adventure Mode: http://www.themmnetwork.com/2013/06/15/so-how-does-mega-man-figure-into-the-adventure-modes-story-in-super-smash-bros/
From a technical standpoint, this is perhaps a very good idea. SSE, along with other game modes he added, took up most of the GB, which is around 5, in Brawl's dual-layer disc, which is limited to 8GB. The roster only took up about 2GB, so now those extra spaces can be used to increase the roster size for the 3DS version, which holds the same amount of GB as a Wii disc.