Given that there are a limited number of spots for standby, I predict that, as a result, people would come extremely early and camp out to snag one of those desired spots in the standby line. I would also expect a dangerous high speed stampede (regardless of how many cast members would caution against running)—unless they do the slow walking behind the rope thing they did for the Cars Land opening to minimize the initial RSR craziness.
From what I have seen on the Disneyworld site describing the policy & procedure experiments & tweaks they did there, they don’t appear to want people camping out at 4am, which is what I’d expect to happen. People who’d come after park opening would end up the same problems they have now, except that instead of no boarding groups left there’d be a maxed out, closed for further people standby lane with people standing there for hours (instead of, as they can do with the current system, go on other rides while waiting for their turn). Why on earth would anybody want that (besides maybe the small number of
DAS people who would get to bypass the line).
I like the current boarding group system and hope that they will still use it when we visit in August. It doesn’t give me a guarantee (nothing is ever guaranteed at
Disneyland, and rolling with the punches is part of the experience), but it would give me a decent chance (and I am saying that as the proud owner of an iPhone 5s with AT&T service—not exactly the racing horse of phones...).
I would hate for it to become a lottery, because I tend to unfortunately do notoriously bad on those.

According to the OC Register, Disneyland has an average of 50,000 visitors per day. If I calculate the current 70 guaranteed boarding groups times (generously guesstimated) 100 persons per group, I end up with roughly 7000 ride slots (more if the ride doesn’t break down, as it currently tends to do every once in a while). That would, in a pure lottery, leave me with only a 14% chance at winning one of those spots, which strikes me as rather crummy odds. Even if there would be more than one lottery with chunks being raffled out & taking part in the earliest one and then again in all later ones would improve those odds (while other people doing the same and more people being in the park in the second half of the day would decrease them). Since the 50,000 is an a average & I’d be there in summer when kids are on break, my odds are likely to be lower than those of somebody who’s there at an off-season weekday.
The worst thing would of course be an advance lottery, similar to what they did for Galaxy’s Edge opening reservations, with a virtually unlimited number of people anywhere (including those not even in the park or not even planning to be in the park but simply entering for kicks) competing for the same limited number of spots.
Yeah, math!