Another thing today's update shows is that there's probably at least two more franchises they haven't announced yet. Look at the filenames for the icons.
http://www.smashbros.com/en_us/images/icon/world_b_01.gif - Smash Bros.
http://www.smashbros.com/en_us/images/icon/world_b_02.gif - Donkey Kong
http://www.smashbros.com/en_us/images/icon/world_b_03.gif - Star Fox
http://www.smashbros.com/en_us/images/icon/world_b_04.gif - Kirby
http://www.smashbros.com/en_us/images/icon/world_b_05.gif - F-Zero
http://www.smashbros.com/en_us/images/icon/world_b_06.gif - Metroid
http://www.smashbros.com/en_us/images/icon/world_b_07.gif - Earthbound
http://www.smashbros.com/en_us/images/icon/world_b_08.gif - Pokemon
http://www.smashbros.com/en_us/images/icon/world_b_09.gif - Zelda
http://www.smashbros.com/en_us/images/icon/world_b_10.gif - Mario
http://www.smashbros.com/en_us/images/icon/world_b_11.gif - Yoshi
http://www.smashbros.com/en_us/images/icon/world_b_12.gif - Fire Emblem
http://www.smashbros.com/en_us/images/icon/world_b_13.gif - Unknown
http://www.smashbros.com/en_us/images/icon/world_b_14.gif - Ice Climbers
http://www.smashbros.com/en_us/images/icon/world_b_15.gif - Animal Crossing
http://www.smashbros.com/en_us/images/icon/world_b_16.gif - Wario
http://www.smashbros.com/en_us/images/icon/world_b_17.gif - Metal Gear
http://www.smashbros.com/en_us/images/icon/world_b_18.gif - Kid Icarus
http://www.smashbros.com/en_us/images/icon/world_b_19.gif - Unknown
http://www.smashbros.com/en_us/images/icon/world_b_20.gif - Sonic
Notice that 1-11 are from SSB, 12&14 are new to SSBM, and 15 onward are new to SSBB. Leads me to believe that 13 is Game & Watch, and 19 is a new franchise.
(Note: This idea has been previously posted on this thread by someone else, but with Sonic's inclusion, we now know that there's most likely another new franchise.)