KiCad is not quite ready to replace Altium for two reasons. The first and biggest is that, as already stated, it simply lacks some features that Altium has. But, nobody necessarily needs to wait for the KiCad developers to implement the feature. No, I'm not talking about the fact that KiCad is open source, so you can modify the source code if you want. I'm talking about the fact that KiCad offers a direct way to implement functionality or integrate with other software through the use of plugins. You don't have to bribe the KiCad developers; specific features are developed by the people that actually need them. So the idea of a commercial company hiring a KiCad developer is only slightly off the mark. If the company has a software development team, then they can task one of its members with building the plugin they need.
I'm not saying that every feature in Altium could be replaced (successfully) with a KiCad plugin, but lots can. There's been requests for integration with a parts database. I haven't tried it, but I'd be wildly surprised if it weren't possible to do that in a variety of different ways with a plugin.
The other reason that KiCad is not ready to replace Altium is that anyone that works with others using Altium need it themselves. As a consultant, when a customer requires me to use Altium I ask for a computer with all the software installed. When I'm done with the project I return the computer. The rest of the time I use KiCad because I don't need the extra features. But, if I did need to buy an
Altium license, then I would probably just use it all the time and not bother with KiCad at all. See the problem? So there's an entire market that KiCad will not penetrate until it can at least open Altium projects, make modifications, and save the project in Altium file format. Maybe that could be done with a plugin?