Board Thread:Sonic Boom/@comment-679780-20150131163852

Apparently this is a confirmed thing now.

Which makes me wonder how canon Sonic Boom: Shattered Crystal is for Knuckles' Hangout being located in the Scrapyard.

Though it could be possible Knuckles is free to leave the island as he pleases as it's not confirmed if he is the last echidna, guardian or if it's even a floating island. 