Initially when i saw the first video i thought that this is just a remaster of sf4... but i was wrong when the screens and the gamersyde video release... there is a massive difference between the character models, details, lighting & effects of the games. I would like to see more detail in the stages but i think that will come over time.
in anycase... i have a feeling that the 16 character breakdown will be:
8 Original Fighters (Ryu, Ken, Chun Li, Zangief, E. Honda, Blanka, Guile, Dhalsim)
4 New SFV Characters
4 Boss Characters
Moveset Changes, Outfit Differences and the overall system will make it feel like a different game entirely.
As for additional characters... I can also see Capcom releasing different packs such as
Street Fighter 4 Pack
Street Fighter 3 Pack
Street Fighter 2 Pack
Street Fighter Alpha Pack
Capcom All Stars Pack
and bring the roster close to or surpassing the Ultra SF4 roster over time.