I have a feeling they'll drop subscription costs for non-legacy. They won't attract new players once they learn they'll be asked to pay more than their friends. Other MMOs don't do that, and, as many threads on the official forums have shown, justified or not, people get mad when asked to pay more for something than other people.
For all the people who (rightly) criticize lifetime subscriptions as "cash grabs" that no firm that was feeling good about their product would do, what does legacy look like? Same thing--if SE felt good about its product, it wouldn't have offered a lifetime reduced fee to its most likely-to-subscribe customers for, what, $45 bucks (plus you get access to the game for that period)? If you play for 5 years, that's $300 they lose out on.