I don't think it'll change too much. There's not enough rides at World Showcase and Epcot in general. Nothing new has been added since Soarin' came to Epcot to disperse the crowds. If they added more new rides earlier, then I could argue the Frozen ride wouldn't be a problem for the crowds!
Soarin' will still be a popular ride and a FP+ or bust ride even with the Frozen ride coming along. Isn't Peter Pan's Flight still a FP or bust ride even with the Seven Dwarfs Mine Train? The vibe that I get is that it's still the case for Peter Pan. If Disney continues to use the tier system for Epcot, the Frozen ride be a Tier 1 in all likelihood. Mayhem would ensue if the tiers were abolished! There'd be absolutely no chance to get Test Track, Soarin or the Frozen ride FP+ slots if that were the case!
And since World Showcase doesn't technically open until 11 am on most days, there's a possibility that people will get in line for the Frozen ride and wait 2 hours in line, maybe 3 hours if they have Akerhus reservations, until the ride opens if they don't have FP+ reservations. So what I'm trying to say is hypothetically, even if you were at rope drop and you were the very first person in line for the Frozen ride, you would still have to wait 2 hours for the ride to open because World Showcase doesn't open until 11 am.
For me, the bigger priority would be Soarin' because it's my favorite ride at Epcot and I can do single rider for Test Track and I've come to terms that a FP+ slot for me for the Frozen ride will be very unlikely in the first couple of years. Soarin' would be my top priority for FP+, otherwise, I'll be at rope drop and head straight there because I know I wouldn't want to wait a long time for that! The Frozen ride may as well be 7DMT 2.0 in a sense that you would be extremely lucky if you got a FP+ reservation for it.
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"All my life I wonder how it feels to pass a day, not above them but part of them.
And out there living in the sun, give me one day out there, all I ask is one to hold forever. Out there where they all live unaware, what I'd give, what I'd dare, just to live one day out there."