As seen in this article by Transport NSW, Opal digital card is being trialled.
Eligibility for this includes paying a full fare adult card so atm not that much different than tapping on with your credit card but it's good to see public transport catching up with the technology.
Hopefully we will see this soon drip down to all Opal cards.
Question is, will you use it or prefer the physical card if you even use Opal anymore