In anticipation of people wanting to discuss/speculate about what is behind the statement that appeared on TrueCrypt's site, I open this thread.
WARNING: Using TrueCrypt is not secure as it may contain unfixed security issues
This page exists only to help migrate existing data encrypted by TrueCrypt.
The development of TrueCrypt was ended in 5/2014 after Microsoft terminated support of Windows XP. Windows 8/7/Vista and later offer integrated support for encrypted disks and virtual disk images. Such integrated support is also available on other platforms (click here for more information). You should migrate any data encrypted by TrueCrypt to encrypted disks or virtual disk images supported on your platform.
I have my own speculation (but that is all it can be), which I will try to post later.