No, Bukkit plugins won’t work with sponge unless they are ported. BlizzardFyre is keeping a list of the plugins that are going to be ported.
The Sponge API has no dependencies, it’s an API afterall. The official Sponge implementation (The thing that you actually use on your server) will be a Forge coremod. That way, Forgemods and (Sponge-)Plugins will be able to work together.