Personally, I think it may be sort of a "throw back" Kirby with colours similar to the Wireless Vacuette and a complete redesign.
The Kirby has "kinda" changed within the last 20 years, but not like it did from the Sanitronic to Classic series, or Classic to Generation. We're past the current trend of Kirby major overhauls so I definitely think we'll be seeing a redesign.
Hopefully a Kirby with a quieter, maybe brushless motor? Only time will tell.
For all we know, we won't see a new Kirby and they'll just keep the current Sentria II (which by the way, is a beast.)