We will know for certain after Thursday, but the bottom line is you will still be able to upgrade, and your net cost will be about the same. It is all math
What's the difference between paying $300 up front with $40 upgrade fee and $20 extra per month for 24 months
Paying zero up front, no upgrade fee, and dividing the full retail price of a $820 phone over 24 months in $34 monthly payments?
It is the same, that is basically the change that is coming.
What irritates me is that I signed up for the Edge plan in December. Now the line access fee is going down from $40 to $20 and I'm stuck paying $40 for another 16 months. I get the $25 credit per month toward my monthly device fee. If I go to the new plan I would only get $5/per month discount when the new billing plans take effect. The Edge plan is marketed with the discount for the device but at this point I'm overpaying for my line access. This change is not fair to existing customers!
That is not the way it will work. The $25 credit was always toward the access fee, not the device.
On your current plan, which you can keep, your monthly access fee is $15 ($40-$25).
If you switch to the new plan, the access fee is $20, no additional discount possible. It is likely cheaper to stay on your current plan, but calculate it out.
The monthly cost of the same phone is equal between the 2 plans.
The big difference is those on Edge or month to month with 6 GB or more of data will have access fee increase $5 per line, if you switch.
Summary, you do not need to change.