Nope.
You can get regular Wigglytuff though.
Simple reasoning: I have done EVERYTHING in this game. Recruited every Pokemon, beat every dungeon, complete the story, and recruit Kecleon. Never once has the Guildmaster said anything about joining.
In depth: The baws has done so much emotional things. I mean, his first Exploration Team was with a criminal. Then Chatot got hurt. He probably cannot handle the stress of Exploration anymore.