I doubt that it'd be anything other than an STMicro ARM device, there's a lot of time/effort invested in the current architectures. So far, there aren't any faster/better STMicro upgrades for the Netduino. 
I would love something in the 1GHz range, to help make up for the overhead of NETMF.
My guess/hope us is that it'll be something in new ultra-low power family. That would allow for long battery life, and solar recharging.
http://www.st.com/we...1/SC1169/SS1295
STM32 L1 series of ultra-low-power MCUs
ST’s ARM® Cortex™-M3-based STM32 L1 series uses ST’s proprietary ultra-low-leakage process technology with an innovative autonomous dynamic voltage scaling and 5 low-power modes offering unprecedented platform flexibility to fit any application. The STM32 L1 series extends the ultra-low power concept with no compromise on performance.
The well-know STM8L is also a member of the ultra-low-power family sharing the same ultra-low-leakage process technology.
More than just ultra-low-power MCUs, the STM32 L1 series offers a wide portfolio of features, memory sizes and package pin counts. Combining ultra-low power and performance, the portfolio covers from 32 to 384 Kbytes of Flash memory (with up to 48 Kbytes of RAM and 12 Kbytes of true embedded EEPROM) and from 48 to 144 pins.
This innovative architecture (voltage scaling, ultra-low-power MSI oscillator) gives your design more performance for a very low power budget. The large number of embedded peripherals, such as USB, LCD interface, op amp, comparator, ADC with fast on/off mode, DAC, capacitive touch and AES, gives the STM32 L1 series an expandable platform to fit all your requirements.
The series is available in 4 different lines: STM32L100 Value line, STM32L151, STM32L152 (LCD), STM32L162 (LCD and AES-128).
To simplify migration and give you all the flexibility you need, the STM32 L1 is pin-to-pin compatible with the different STM32 F series and opens the door to the full STM32 ecosystem.
o) Ultra-low-power mode: 300 nA with backup registers (3 wakeup pins)
o) Ultra-low-power mode + RTC: 900 nA with backup registers (3 wakeup pins)
o) Low-power run mode: down to 9 ?A
o) Dynamic run mode: down to 230 ?A/MHz
BTW, ST is having seminars and attendees get a free eval kit (if you can take the time off from work).
http://www.st.com/we...w_power_seminar
