It will be too late when the FBI tries again
Apple is treating this as a warning shot and has redoubled their efforts to make their devices and user data secure. Now they know they must keep user data secure against even themselves, lest the FBI order them to hack their OS! The next time the FBI tries this on Apple, perhaps with a newer model of iPhone running a later version of iOS that includes these changes, Apple may be unable to help them - even their code and signing keys won't help if its impossible to install a new OS onto a locked phone - which it will be no later than iOS 10.
And others will follow. Some companies may have limited options to do so: Facebook and Twitter can't encrypt regular posts since they have to be readable by the world, or at least hundreds of people. But they might secure Facebook Chat, WhatsApp, and Twitter DMs.
Google and Microsoft will be interesting wild cards. Google should want to secure everything, but securing everything so even they can't read it will ruin their data collection ability, so they probably won't. Microsoft could add a lot of security to the world if they allowed (or especially defaulted to) encrypted volumes for Home versions of Windows. They've previously considered that an enterprise capability, maybe they will rethink that position.
So what then, does the FBI lobby congress for a law that makes selling a phone with that level of security illegal? That would be like their failed strategy of treating encryption as "munitions" back in the 80s and 90s, thinking they could keep the genie in the bottle. If they deny Apple the legal right to sell secure phones, some company elsewhere in the world will (probably with an Android fork that locks Google out of all that juicy data, hurting them too)