Well, here's my takes on what he'll sound like.
1) He'll be entirely mute and his "voice" will be sound effects from the Kirby games.
2) Makiko Ohmoto will voice him, but he will only speak gibberish and grunts. Mrs. Ohmoto is quite a talented actress; she voiced all the characters in Return to Dream Land, including Dedede and Meta Knight. She also voices Ness.
3) They'll give him a voice similar to Waddle Doo's voice in the Japanese dub of the anime. Not the silly, gruff English voice.
4) Although highly unlikely, Bandana Dee will be voiced by Escargoon's voice actors, both in Japanese and English. They'll give a new spin to Dedede's sidekick.