Cutting Room Floor is a website known for posting unused and cut content, and yesterday they were able to verify that both Ryu and Roy DLC theme files are inside the 3DS version of Super Smash Bros.

They tweeted this out confirming the files existence. To be clear, this only confirms that the sound files are indeed on the cartridge and whether or not they will be in future DLC is yet to be determined. You can listen to the discovered files here.