Very old really, especially if you are tuned into the business enough to see where technology is going. The combination of SoC, 3d technologies and very high speed busses will lead to much smaller foot prints while increasing performance. So if Apple has to redesign the Mac Pro, I believe they have no choice here, then they need to look towards the future not the past. Another tower would basically say that Apple is stuck in the past.
The question really becomes is it time to shake up the product mix and debut radically new hardware. One look at both the Mini and the Pro tells me yes. In fact they are over due in my mind. Both platforms are grossly over priced and in some ways I see the Minis pricing to be the worst of the two. Interestingly I suspect the use of Intel hardware plays a big part in pricing this hardware out of the market. Then again AIRs are very competitive so maybe Apple has gone stupid here. In any event the point with pricing is this, people can only put so much value into Mac OS, so an additional $100 isn't death to a product rather it is the multiple hundreds that kill these products.
So what are Apples options here, it is either cut margins or redesign. Apple, could redesign both platforms to be attractive in their product categories again. That means priced within a reasonable value for the markets served and in line with competitive hardware. There are many avenues but one consideration for the Mini has to be AMD hardware. That if you think a Mini is even worth keeping.
I'd love to see a much smaller Mac Pro, but I haven't seen Pro GPU's get much smaller. The things are huge. So their either has to be a huge change in the way graphics are pushed to monitors, or there's going to be a design limitation based upon the huge GPU's we have these days for Pros. I'd really like to think that Jonny Ive could put together something jaw dropping, while keeping performance the priority for Pro users. I can't complain about my Mac Pro; I love the thing, and even being several years old, it still chews through high definition video with ease. If they can drop the size to something like Steve's Cube, I'll certainly drop the plastic for it.