My guess is they will go with there being a delay between when you can buy the full digital copy (day & date) and when it shows up in the subscription. So people who want to read what is out now pay the individual price.
This is fine for me. I don't feel the need to read a comic book the day it comes out as long as I can get it sooner or later. Hell, I'd be fine with a month delay if it would make them happy. More than that would probably be too long.
It'll take them a while to hammer out a pricing scheme that works for their bottom line and works for us consumers. I think a tiered subscription would work:
No subscription - you can still buy digital comics a la carte, pay full cover or almost full cover.
Subscription A (cheapest)- archive comics only (only issues older than a certain arbitrary date)
Subscription B - modern comics only (only issues more recent than certain arbitrary date), new releases are delayed from street date by a day, a week, whatever works out
Subscription C - all comics, new releases still delayed
Deluxe Sub - all comics, new releases same as street (or less delay, or something)
The key is to either trick the customer into perceiving a value for the subscription, or actually providing a value, whichever comes first.
Another option would be to provide a la carte subscriptions for titles, the way you can get the real book mailed to you. So if you really only care about Spider-Man, you could pay a lesser total dollar amount to receive only Spider-Man books, although the price per issue would obviously be better on the general subscription.