The variable vane turbos are not the future (IMHO), they're complex and costly, see prices on them and rebuild costs. Variable geometry turbines are the future...
Varbiable geometry turbine housings are a much simpler and cost effective solution, such as what's found on the new breed of VGT3xx, 4xx, and 5xx series from Holset. They have a moving housing that actuates based on a number of inputs to the control unit such as RPM, Throttle position, Boost level, etc (full list availble on Holset's site). This is the way of the future IMO because it solves the down low boost issue of a turbo because you can operate it at peak efficiency from idle to max power with the correct application exhaust housing geometry. Now it will never be quite as efficient as variable vane because that prevents flow separation around the vanes due to correcting the vane angle for a given flow rate but it is simpler, costs less to implement and the only penalty is some added weight to the turbine housing (10-20lbs heavier, not too bad a tradeoff for the simplicity, read reliability, of the design).
There's a fella, Aero, who's on multiple other boards (DSM Tuners, TurboTalk, TurboFord, etc where this debate has raged) has a VGT3XX series on his DSM and it produces significantly better boost results down low than a traditional turbo. The only thing is since no one has been able to figure out how to control it with the OEM controller he's got a manual wastegate on the actuator arm to open the turbine section as boost builds to prevent overspinning but at the same time not open to fast to have a huge lag. This form of manual actuation is cool and alternatively you could give yourself some neat capabilities with it. Say for instance you wanted 3 different tunes, one for drag, one for autoX, one for street, you could add a stepper motor to 'preset' the initial turbine housing size to give you quicker boost response, slower boost response, or something in the middle. Add a MegaSquirt or other stand-alone with one of those nifty aftermarket LCD interface controllers that can carry multiple tunes and you could have multiple 'turbo/tune' options at the flick of a switch. Or figure out the best variable setup and have all the low end boost of a supercharger with the peak power of a turbo, with the efficiency of a turbo, and the ease of temperature control of a turbo, albeit with more plumbing...
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