Based on Konami’s hint here, it looks like the Special Guest will be related to Aquos (Neo-Spacian Aqua Dolphin). Usually we don’t indulge too much in speculation, but what can likely be presumed here is this has something to do with either:

Jaden from Yu-Gi-Oh! GX, i.e. Matthew Charles.

or a character also voiced by Aquos’ voice actor, Oliver Wyman.