Thanks for all the information.
I am not sure I understand the below but it seems like a good question as I am unfamiliar with how this works. It does sound like I will need to activate it on my wife's line phone first.
I called *611 to see about an early upgrade and customer service said I needed to go to a store as I am about 7 days outside the 30-day early upgrade window. I told her I wanted to order a phone available only online. She then told me to call telesales and ask about an early upgrade. I will have to do that tomorrow. I am going on vacation next week so I am hoping to get it early to play with it while on vacation.
By SIM adapter, I use this ->
Amazon.com: Nano to Micro/Normal SIM Card Adapter for Apple iPhone 5 4S 4G 3GS 3G: Cell Phones & Accessories to take the Nano SIM (smallest, used in iPhone 5) to either Micro SIM (used in S4, Lumia 928, Z10) or regular SIM (used in my Bionic and Thunderbolt). NOTE: some users of sim adapters have reported damage to the phone's slot/pins, use at your own risk!
So you could use the Nano to Micro adapter in that pack to put the iPhone 5's sim into the S4 when it gets there. No need to go to store, do anything funky, etc. Then just remove the adapter and put the nano SIM back in the iPhone 5 after a day (to give VZW's system time to see the phone switch). The S4 would then be free to use on any line.
My only problem is.. I don't know if, for the upgrade to be fully realized in Verizon's eyes, you must use BOTH the new phone and SIM card to activate it. Of if you can just move your exiting SIM into the new phone.
If you MUST use the SIM included with the S4, since it and the iPhone 5 use different sized SIM cards, it gets a little "messy"... you'd have to activate the S4 on Wife's line with the included Micro SIM. Since the SIM cards are "once and done", to put the iphone back on that line, you'd have to visit a VZW store for them to give you a new nano sim and put the iPhone 5 back on that line. If your nexus uses a Micro SIM, you can just move it from the Nexus to the S4. If your Nexus uses a "full" or "regular" size sim, then you need to get a new Micro SIM from Verizon to switch to the S4 on your line.