Your current contract will have this information.
Their is no way to know if the next lot of plans will have this or not.
All the information is in the CIS document thats available when you either log into your optus account online or via their app on your phone.
I take it you are leasing and expect to hand your old phone back? As you are past the 12 month point you can upgrade to a new phone anytime now. As usual you'd just pay the $99 upgrade fee. That said, I'm not sure that if you wait the full 24 months then you won't be charged the early upgrade fee. Might be better to wait until Novenber.
Although Optus can add remove plans this would seem to remain unchanged. You can look up your iPhone and the monthly plan options and prices moving forward here. Read the CIS at the bottom for additional info. You'll probably find the prices have gone up unfortunately.
But note that if you are currently on a lease then you have to hand your phone back this time. Next time (in Nov 2021) you will be able to keep the handset. This gives you the options or:
1) Selling it for say $1000. Recontract with Optus for another new phone and set off again.
2) or keep using it and move to a much cheaper SIM only plan