The updates will continue, but unless any streaming have made the phone hold on to the Wi-Fi it will be done through 3G data.
The phone is designed to run with a data plan and it sucks if you don't have one. But for now you only have to accept that Microsoft designed it to be convenient to the 99% of Smartphone users with dataplans.
Does AT&T use specific data plans for each phone OS?
For instance, is there a specific iPhone data plan, a specific Wp7 data plan, Android specific plan, Blackberry specific plan, etc...? Or is it just one universal data plan?
Universal for SMARTPHONES pretty much
$15 for 200 mb
$25 for 2 gb
$45 for 4 gb 4G tethering.
So will my grandfathered unlimited plan that I got with my iPhone, still carry over to my Windows Phone?
I have no idea.