There can be both. White is so long in the tooth now.
There reaches a point in design where an item has 'intrinsic' beauty regardless of it's age, contemporary influences or it's functional intent. Like say the Porsche 911 whose iconic form arguably reached it's emotive zenith in the 1973 Carrera RS.
The current white iMac is , IMO, at such a crossroads ;
Does it continue on evolving what is an elegant, beautiful and functional design or do they 'throw it all out' and start again ?
Porsche attempted the latter with the 924/928 in the eighties and they were a total failure. They had a stated intention to stop building the 911. Customers rejected the idea!!
To this date the essence of the Porsche 911 is what drives that company. Even today if they stray too far from the expectation of it's design customers simply reject the design and sales plummet!.
I think Apple has a similar 'business model' with the 1984 'Mac' defining the direction that Apple have yet to be able to steer from - and in all probability with good reason since the 90's beige boxes nearly ruined the company in the way that the 924/928 nearly ruined Porsche.
Sometimes you do not need to have an endless stream of 're-invention' - you just have to recognise what's great and build on that.
That design is 'the white iMac'.
My feeling is they will keep the white ( perhaps introduce a piano black as an option) but just slenderize and sleekify...
Why break a 'design classic.