Those vendors will follow. As they have previously when they transitioned from powerpc to x86. Games is a good point. But this is not a big thing on MacOS (as yet) anyways. If it saves hundreds of dollars per machine, its a no-brainer for the vast majority of users.
Intel chips blew the doors off PPC by the time Apple got around to the PPC -> Intel transition. That (and good emulation software) allowed a relatively pain-free transition for most consumers: PPC apps didn't feel any slower when run on a new Intel-based Mac. That made it fairly easy to accumulate a critical mass of users with Intel systems, yet it still took ages for native apps to become available from the likes of Adobe and others.
Fast forward to today.
ARM chips are, at best, a little slower than the Intel chips they would replace. On top of that, the x86 ISA has a reputation for being hard to emulate well. So put yourself in the shoes of the consumer: are you going to upgrade to the new ARMBook Air, if it runs all your old apps at 1/2 or 1/4 the speed (and I'm being super optimistic here) they ran on your old MacBook Air? No! You're not! You're going to stick it out until the second generation of ARMBook comes out.
That means no critical mass of people who own ARM-based Macs and are willing and able to pay for native ARM software. That means vendors will. not. follow. This doesn't even take into account that Apple have burned their bridge with Adobe (a major vendor of 3rd party software for Mac).
Last point: I think you're wrong about games. There are tons of games for Mac on Steam. Would vendors go to the trouble of making a Mac port if there was no money in it?
It took a VERY long time for the large ISVs to switch, and while games aren't big on OS X many people like the fact they can boot into Windows to play them.
If Apple was able to get the performance of their chips up to the level of Intel chips, would they be able to save hundreds per machine? Intel has some very large economies of scale.
If Apple wanted to save hundreds per machine they could do that right now. Intel's marketing campaigns that Apple doesn't take part of (like the 'Intel Inside' stickers) come with large rebates. Apple could use that and not have to go through the huge pain of another architecture switch.
