currently I'm on the $89.99 home bundle. (unlimited interwebz, local, national and mobile calls)
it's good.
however cable is being discontinued and NBN will be available.
unfortunately the NBN equivalent home bundle is more expensive.
has anyone been successful in retaining the old pricing when they are forced onto NBN?
"Negotiate" with Optus. i.e State that you wish to remain on cable and if they can't do that for you, you'll find another provider who can. Compare the market, see what's out there. Note down other cable providers with similar perks and their prices and use that as the basis for your argument.
Always remember to be polite. The guy/girl on the other end is most likely would have their hands tied by Optus in terms of negotiating. They're human too, screaming never helps. If they can't help you, ask to talk to a higher authority figure, they'll have more power to help you secure a deal. If you've been with Optus for a long time, they most likely would want you to stay.
The best possible outcome would be Optus transitioning you from cable to the NBN whilst you continue to pay $89.99 a month and keep the perks you have. Do your homework, be polite and be patient. Good luck!