Is fuchsia going to replace Android?
No, Google Fuchsia will NOT replace Android OS. There have been speculations that Google Fuchsia will replace the Linux Kernel in Android. But from Google's investments into porting Android apps to Chrome OS (Linux Containers), it would seem there is no plan to replace the Linux Kernel either.
Pink + Purple == Fuchsia (a new Operating System)
Is fuchsia OS open source?
Yes, It is open-source, real-time operating system.
Is fuchsia OS is Linux based?
Fuchsia is not a Linux based OS like Android and Chrome.