I can't imagine that most developers will do more than bump up the settings to a level that plays comfortably on the Neo. I mean, what's in it for them to do more than that? A sale on the PS4 is (probably) the same as a sale on the PS4.5.

However, I'd also bet that Sony will offer some nice advertising incentives to developers who go the extra mile in terms of enhancements. First party developers will probably have that as a mandate.

Without a doubt devs will do as little as possible to begin with. Perhaps The Witcher 3 will still be 1080p/30fps but it will hold 30fps constantly even in the swamps. I think we'll see a few games with small improvements like this, but I think Sony will keep a close eye on the situation and make sure eventually devs make more of an effort.

"Now the roles have been reversed--Sony's new PlayStation 4.5 is the company's pre-E3 2013 Xbox One"

Exactly!

...only with the difference that Sony is making the new hardware features better instead of worse for the consumer

Ah I see. I thought it was if they made a Neo mode then it had to be at least 1080/30. But they could still release it as a base 900/30 and it still be playable on the Neo.

Yes. All games after October must have a Neo mode and must show at least 'some' improvements over the standard PS4. Any games released prior to October are not under any mandate but can be patched if the devs want to. Of course ALL games are likely to be upscaled to 4K so even older games will look better on your 4K TV.

I think Sony should then go with the way I thought it was then. That way it's only a pain in the arse for the devs if they choose it to be and they won't be hated by everyone. If rumours are to be believed that is.

But if devs could just put out the same game there wouldn't be a need for the Neo. I think Sony have struck the best possible balance. All devs have to do is give people enough reason to get the PSNeo and that could be very simply a resolution upgrade or framerate improvements. Devs moan about everything from what I've been watching over the years. When they make a PC version of a game they have to account for dozens and dozens of different configurations but with the PS4/Neo all they have to offer is TWO. We're seeing a few games now with dynamic resolution, like DOOM for instance. All the devs have to do to make it support NEO mode and meet the mandate would be to make it native 1080p across the board.

I wouldn't be surprised if developers still only make 2 versions one that would run on both Xbox One and PS4 and a version that runs on PS4.5 that way they are still only putting the same time/cost into balancing 2 version rather than an extra version. But the downside of this is early adopters of the PS4 get shafted into having the worse version like the Xbox One gets.

Not really. This might, however, mean that games that were PC and PS4 only will now be PC, PS4 and XONE supportive... 

I still don't see how to come to the conclusion that all games after October must have a NEO mode.

All I gather from Eurogamer is that Sony wants to strongly encourage developers to include a NEO mode, by not allowing any NEO patches for games released after October. The rest of the article goes on what a NEO mode can't do.

Again further on
Sony is very keen on developers supporting both systems simultaneously, and is motivating developers to ensure that there is Neo support in all PS4 titles from Q4 onwards this year.

Still not required, nor what improvements there must be apart from 1080p and fps >= ps4 version. Motivating is not mandating.
We'll see in October what NEO mode is actually going to be in reality.