The previous form factor (silver tower) lived from August 2006 to December 2013. If we see that kind of longevity out of the black cylinder form factor, I'd be thrilled (although preferably with more internal updates). However, there's nothing stopping us from adapting our design to whatever new models come out.
We have current rack designs for Mac Minis and Mac Pros now, and we can add a third if the need arises.
Consider Mac Rumor's lifespan of the various Mac Pro models: http://buyersguide.macrumors.com/#Mac_Pro
The previous form factor (silver tower) lived from August 2006 to December 2013. If we see that kind of longevity out of the black cylinder form factor, I'd be thrilled (although preferably with more internal updates). However, there's nothing stopping us from adapting our design to whatever new models come out.
We have current rack designs for Mac Minis and Mac Pros now, and we can add a third if the need arises.