I've seen on a couple of sites in the past two days the statement that the goal for Djed is to become the coin with which all transaction fees on the Cardano network will be paid. Since this is the first I've heard this, I'm skeptical. Can someone point to a statement from IOG that corroborates this?
That's not true. For the security of the system, the fees needs to be paid in ADA.
You might use Djed as a way to pay for the fees with babel fees but that is several years away, if it ever gets implemented in the first place.