Hackers have found sound files in the demo. I'll put the interesting ones in the spoiler: http://pastebin.com/NgJ4vPZh
STRM_ME_CON_DRESSUP (pokemon dress ups like in DPP returning?)
STRM_BGM_BATTLE_RESORT
STRM_BGM_BATTLE_TOWER
STRM_BGM_VS_BFRONTIER
STRM_BGM_VS_COBALION
STRM_BGM_VS_DEOXYS
STRM_BGM_VS_FLARE (could be left over from X&Y???)
STRM_BGM_VS_FLARE_BOSS (could be left over from X&Y???)
STRM_BGM_VS_GIRATINA
STRM_BGM_VS_GYMLEADER
STRM_BGM_VS_GYMLEADER_SG
STRM_BGM_VS_GYMLEADER2 (the 2 could be a gym leader rematch??)
STRM_BGM_VS_HEATRAN
STRM_BGM_VS_UXIE
STRM_BGM_VS_SUIKUN (Suicune?)
STRM_BGM_MIRACLE_TRADE (idk what a miracle trade is)
(i also saw ones for lugia and dialga and zekrom but I didn't include them since we know about them being in the game anyway)
Oooooooh that 4th one though!