This keeps coming up so let me clarify please. We understand you have invested time and money into a design and you want the upgrade to be as simple as possible. After all, we also have designs and we understand the pains of updating hardware and software.
First of all, all of our commercial products come with 10 year guarantee promise. We are not asking you to upgrade today. Also, we are ready to help you with any hardware and software changes. There might be a fee and might be free, depending on your project and purchasing volumes.
Software: Updating NETMF to TinyCLR is very easy, but do not take my word for it, look at what Dave had to say
Hardware: We have designed TinyCLR 2.0 to be modern and secure. This unfortunately has ruled out old CPUs. G400 for example used SAM ARM9, a very old and non-secure micro! You simply will have to use the new SITCore hardware in your designs. Sometimes there is no change at all, like if you use G400D because the new SC20260D is a drop-in hardware replacement. But unfortunately, sometimes you have to change your circuit, like if you are using G400S.
Here is a lookup table with suggested replacements:
G30 and G80 => SC20100 (LQFP100 but the pinout is not compatible: PCB changes are necessary)
G120 => SC20260B (99% compatible drop-in replacement)
G120E => SC20260E (99% compatible drop-in replacement)
G400S => SC20260E (not compatible, PCB changes are necessary)
G400D => SC20260D (99% compatible drop-in replacement)
UC25 and UC55 => SC20260D (very close but not compatible, very small PCB changes are necessary)
Please go ahead and ask for further clarification if necessary.