I would suggest moving to the loyalty plan before you do the upgrade. To be eligible for the loyalty plan you have to be within the last four months of your contract or out of contract. Upgrading your lines first would cause you to become ineligible for the plan. So I recommend changing your plan now, well before your upgrades come up. You won't be required to change your plan again after upgrading, so you can remain on the loyalty plan.
Also, later on, when you decide to add that third line it won't affect the plan.
To be eligible for the loyalty plan you have to be within the last four months of your contract or out of contract.
This may be the general rule, but not always??? I just upgraded in May and hubby upgraded end of june. We are moving to the loyalty plan w/our next month start of 8/7.