Seriously dude, what the hell? You keep making this huge assumption, why? You say it's not simplistic and then you post that?
Firstly the ps4 and ps4k are going to be running on the same OS. What that means is that developers will not necessarily have to code 2 entirely different versions for the 2 SKU's but rather it will be a single version with device detect running. Once the software has determined whether you are running the game on a regular ps4 or the ps4k it will then select the appropriate configuration which have been pre-determined by the developer. This "extra work" you speak of is likely to only come into play at the optimisation stage of development. This is how it works in PC development and iOS/android development. To get the extra optimisation work done they might employ a few more people or outsource it. The complexity of this largely depends on how Sony handle things in their SDK. It doesn't need to change how things are done earlier on in the development pipeline as assets are generally created in much higher quality than necessary and in most cases there will also be a PC version in existence which will be able to take advantage of the higher quality models/textures/environments anyway.
Now of course, some developers might want to go the extra mile and do something special (limited to visuals) for the ps4k version but if this is the case they would be wise to build/create a small team to do so. It does not necessarily mean that they will pull people away from the regular ps4 version in order to achieve this, they might get some people in on a contract basis or even outsource this portion of the work. This commonly happens when developers want to do an extra SKU of a game they are making but do not have the in-house capabilities or resources in order to do so. Again, this commonly happens with PC ports of console focused games or even last gen ports of the game is cross gen.
It will be a similar story for Microsoft due to them having developed UWP for this very purpose. The only debate around UWP at the moment is whether it's a model that is also suited to the PC environment which is something they are attempting to force at the moment. For console/mobile applications it's perfectly fine however.
Based on your agruement we should all be pushing for every single game in existence to be exclusive to ensure no resourses are wasted in making multiple versions of the same game.
Yeah I don't get this complaint either. The PS4K, by all accounts, is running the exact same hardware configuration but with more CPU and GPU speed headroom. I can't believe that the drivers wouldn't be common, either.