What is the status of Casper FFG within the ETH 2.0 roadmap. Is the plan still that it will be implemented with Phase 0 or Phase 1? Or is the plan to adopt Casper CBC instead, and forgo implementing FFG at all?
Yes, Casper FFG will be implemented in Eth2 phase 0.
Most Eth2 client teams have already implemented the Eth2 variant of FFG and all public Eth2 testnets are using it.
Some recent information about Eth2 and FFG can be found in Combining GHOST and Casper.
There is a long-term plan to switch to Casper CBC, however serious specification or engineering works have not started.