Street Fighter V won't make you pay for additional characters. *Pause for dramatic "yay"-ing*
The announcement that all Street Fighter V gameplay related post-launch content would be earnable instead of just buyable was made during Capcom's EVO 2015 panel, and shared afterwards in a PlayStation blog post.
"Street Fighter V will be the first iteration in the franchise where it is possible for dedicated players to earn all gameplay related content (such as characters) for free, simply by playing the game," Capcom's Community Manager Peter Rosas wrote in a blog post. "Long gone are the days of forced Super and Ultra upgrades! Enjoy free balance updates as soon as they become available, and find and choose the post-launch characters that you want to get."
Street Fighter V will feature two different forms of in-game currency: Fight Money, which is earned by playing the game, can be used to acquire new post-launch gameplay content, such as characters. Zenny, on the other hand, can be purchased with real money in order to immediately gain access to post-launch content. It is not immediately clear what must be done to earn Fight Money (my guess would be win) or how much Zenny will cost.
Later phases of the beta will be used to test the currency in order to ensure it "works in a fair way for everyone."
The game will launch with 16 playable characters, four of which will be brand new to the franchise. "Post-launch, we will be adding new characters to the roster on a continuous basis, which will provide new content for players to enjoy," Rosas stated. "Again, every post-launch character released will be earnable for free through gameplay!"
Street Fighter V will be hitting PlayStation 4 and PC in Spring 2016.