Yes, that discount is because you're no longer subsidizing a phone with your plan anymore. Since these new plans don't subsidize your phone, I would put money on you not being able to receive the $25 off-contract discount anymore on the new plans.
I can't speak to the "new" $20 line access plans, but for the $40 line access plans (More Everything Plan), you can receive the discount by taking the phone off contract. This can happen as soon as you're eligible for an upgrade, although they won't tell you about it because they want that extra $25 a month.