If Microsoft changes drivers associated with the bios and development tools to require TPM, there won't be bootleg versions. Without TPM, the OS simply won't boot. Sure hackers could fix all 600 or so places where the OS contacts TPM this month, but next month it will fall apart again.
I don't think Microsoft has much choice here. After recent malware hacks, Microsoft is becoming legally responsible for insecure machines. Supporting the older CPU's is too costly. There are too many known security holes,.