I challenge the assumption that graphene can be a replacement for gold in most of its applications. Gold has a chemical and physical properties that in no way can be mimicked by graphene, particularly in medicine.
Each element is unique in its chemical and physical properties. In the future, I think that all rare elements will be valuable because we will find specific technological applications for them that can be mimicked by no other element. Many elements unfamiliar to most people have important uses in alloys and catalysis, where no other element performs as well. For example, scandium is used in strengthening aluminum alloys, despite the difficulty of economically mining it. Rhodium is one of the rarest elements in the Earth's crust, but it is used in particular kinds of catalysis. Due to the craziness of chemistry, osmium tetroxide is a gas, which can be used to stain samples for electron microscopy (because it is has a high atomic number and hence many electrons).
Graphene is a form of carbon, while gold is an element. Even if graphene were superior to gold metal in all of its applications (which it isn't), graphene could never replace gold compounds in their applications. Gold compounds have been used since the 1930s to treat rheumatoid arthritis. Although their use for this treatment is waning, the use of gold compounds might be important in some future drug against some future ailment (COVID-19?). Platinum anti-cancer drugs are commonly used today, and some gold-based anti-cancer drugs are currently being investigated. It might be noted that these gold arthritis drugs work by forming gold metal, but the water-soluble gold compound is needed to deliver gold.
The chemistry of gold is gives it promise for many medical applications. One of the reasons that there are so many papers about medical applications of gold nanoparticles is that the surface of gold particles can easily be conjugated to whatever organic molecule you want by thiol (SH) chemistry. Gold quantum dots can be designed to absorb light at particular wavelengths, which could be used in photothermal therapy (targeting and heating specific parts of the body, like cancerous tumors). Attachment of hydrophilic groups by thiol chemistry (or other means) can allow gold nanoparticles to be water-soluble, so that they can travel through the blood stream.
While graphene quantum dots can be made to absorb particular wavelengths of light by nitrogen doping, making graphene water soluble while maintaining its optical and electronic properties might be impossible. Chemically attaching anything to the basal plane of graphene is difficult and ruins its electronic properties.
Gold is also very dense (it's high atomic number means it has a lot of electrons) and can easily be seen by electron microscopy or x-ray images. Graphene is made of a light element (carbon) and contrast with biologial materials (made of oxygen, carbon, hydrogen, nitrogen) is very difficult.