Systemd's fate will be decided by whether or not it works
I have recently been hearing a bunch of renewed grumbling about systemd, probably provoked by the release of RHEL 7 (with a contributing assist from the Debian decision for it and Ubuntu's decision to go along with Debian). There are calls for a boycott or moving away from systemd-using Linuxes, perhaps to FreeBSD, for example. My personal view is that such things misread the factors that will drive both sides of the decision about systemd, that will sway many people either passively for or actively against it.
What it all comes down to is that operating systems are commodities and this commodification extends to the init system. For most people, the purpose of an OS, a Linux distribution, a method of configuring the network, and an init system is to run your applications and keep your system going without causing you heartburn (ideally all of them will actually help you). For (some) management and organizations, an additional purpose is making things not their fault. Technical specifics are almost always weak influences at best.
(It is worth saying explicitly that this is as it should be. The job of computer systems is to serve the needs of the organization; they can and must be judged on how well they do that. Other factors are secondary. Note that this doesn't mean that other factors are irrelevant; in a commodity market, there may be many solutions that meet the needs and so you can choose among them based on secondary factors.)
This cuts both ways. On the one hand, it means that generally no one is really going to care if you run FreeBSD instead of Linux (or Linux X instead of Linux Y) because you want to, provided that everything keeps working or at most that things are only slightly worse from their perspective. On the other hand, it also means that most sysadmins don't care deeply about the technical specifics of what they're running provided that it works.
You can probably see where this is going. If (and only if) systemd works, most people won't care about it. Most sysadmins are not going to chuck away perfectly good RHEL 7, Debian, or Ubuntu systems on the principle that systemd is icky, especially if this requires them to step down to systems that are less attractive apart from not having systemd. In fact most sysadmins are probably only vaguely aware of systemd, especially if things just work on their systems.
On the other hand, if systemd turns out to make RHEL 7, Debian, or Ubuntu machines unstable we will see a massive pushback and revolt. No amount of blandishment from any of the powers that be can make sysadmins swallow things that give them heartburn; a glowing example of this is SELinux, which Red Hat has been trying to push on people for ages with notable lack of success. If Red Hat et al cannot make systemd work reliably and will not replace it posthaste, people will abandon them for other options that work (be those other Linuxes or FreeBSD). And if systemd works well only in some environments, only people in those environments will have the luxury of ignoring it.
That is why I say that systemd's fate will be decided by whether or not it works. If it does work, inertia means that most sysadmins will accept it because it is part of a commodity that they've already picked for other reasons and they likely don't care about the exact details of said commodity. If it doesn't work, that's just it; people will move to systems that do work in one way or another, because that's the organizational imperative (systems that don't work are expensive space heaters or paperweights).
Sidebar: The devil's advocate position
What I've written is only true in the moderate term. In the long term, systemd's fate is in the hands of both Linux distribution developers in general and the people who can write better versions of what it does. If those people are and remain dissatisfied with systemd, it's very likely to eventually get supplanted and replaced. Call this the oyster pearl story of Linux evolution, where people not so much scratch an itch (in the sense of a need) as scratch an irritation.