Yep, it probably means that the character of Bayonetta will pop up in the upcoming 3DS and Wii U Smash Bros. games. This, of course, would not be the first time a "non-Nintendo" character appeared in a Smash Bros. game. For example, Snake from Metal Gear and Sonic from Sonic the Hedgehog appeared in the Super Smash Bros. Brawl. Hey, Sonic is a Sega character, just like Bayonetta!
If Bayonetta does appear, she'll probably be a secret character. Her appearance would be in line with what Platinum Games said about growing the Bayonetta brand and having it reach more gamers via Nintendo.
There is ground for this speculation: Earlier this past spring Masahiro Sakurai, the creator of Smash Bros., visited Platinum Games. He took the following photo:
Of course, none of this has been confirmed. It's all speculation—but pretty good speculation, I think.
And since Namco Bandai is developing the new Smash Bros. games, don't be surprised if Namco characters also pop up—and Bandai ones, too!