The Xbox One is a PC, therefore porting games from Xbox One to PC and visa-versa is simple as directx binds the two platforms. 

In other words, once a developer makes a game using directx, the game can be simply ported to Xbox One.

When a developer makes a game using directx, they are not only developing a game for millions of PC gamers, but also millions of Xbox One gamers. 

From a developers standpoint the install-base is not just that of Xbox One but also of the PC. Which is a win-win situation for Microsoft and Xbox One gamers.

Now I see this as an advantage for Microsoft when luring developers to make games exclusively for directx platforms (Xbox One and PC).  

This is why I think Phil Spencer said the Rise of the Tomb raider deal had nothing to do with the install-base of the Xbox One vs PlayStation 4.

This is also why Rise of the Tomb Raider for PC was set to release shortly after the Xbox One version, because the game was already done for the PC.

I see this trend continuing for the rest of this generation and Rise of the Tomb Raider is just the beginning.

The xbox one is a pc?? Really?....

The answer is no. There is no magical dx 12 or cloud or extra processing core and alas there is no magical PC hidden inside the xbox one.

If that is the trend that is going to continue that is bad news for most. I think Microsoft got some bad press and bad advertising from the Tomb Raider fiasco. Especially when the game will release far after on PS4 and most likely double or triple (if not more) the sales it had on XOne and PC combined.

It doesn't have to. It already is an above average non gaming laptop as far as I know and it's GPU is still stronger than anything without an external graphics card...

It's still running an stone age API from W7 rather than W10...

We are actually seeing the opposite occuring here, with more games either being timed-PS4 exclusive(on PC too) or permanent-PS4 exclusive(on PC too). No Man's Sky is only coming to PC and PS4. King of Fighters XIV is at least a console exclusive for PS4 with the possibility it will come to PC. Street Fighter V is a PS4 console exclusive with no Xbox 1 release for the entirety of the "V" lifespan(no Super/Hyper/Ultra Street Fighter V on Xbox 1). Hideo Kojima's next game is PS4 console exclusive at the very least, unsure about a PC release. Detroit Become Human is PS4 exclusive. Ni-Oh is PS4 exclusive, Wild is PS4 exclusive. Deep Down is PS4 exclusive if it ever comes out. These are only some of the many games that  are not coming to Xbox 1. Not saying the Xbox 1 doesn't have permanent third party console exclusives(Scalebound, the next Worms(???), Quantum Break, Recore), just saying the PS4 dwarfs it in comparison. I don't think we will see any more major Xbox 1 third-party timed-exclusives after Tomb Raider personally. Permanent exclusivity/ timed-DLC/exclusive marketing rights ala Fallout 4 for sure, but no outright timed-exclusivity.

What a load of rubbish.

It's quite clear you have no experience of game development.

This is the future of Xbox and Windows 10 but will it will happen completely this gen probably not but the Next Xbox console will have all the PC library and be running on the exact same platform and require development for for just the one platform, The long term future of Microsoft's platforms is very positive and potentially very strong as the infrastructure is there in the long game.

What?

1st - All games are made on engines that also work on PCs because games are made on PCs.
2nd - An engine is made to support multiple APIs (DX, OGL, etc.). So if anyone is concerned about APIs, it is engine programmers and not game devs per se, and unless you plan to only create Windows platform games ever, you want to go with multiple APIs.
3rd - Unlike Directx, OpenGL is crossplatform, if with Directx, you can make games for Xbox and Windows, with OpenGL you can make games for Windows, Playstation, Wiis, Linux and Mac and that makes it easier and cheaper to access a way bigger possible audience.
4th - When it comes to Console > PC port and viceversa, it is mostly about hardware and driver optimization (specially for PC), not about APIs..
5th - It seems to me like the OP is daydreaming.

Yes that is why people are making PS4+PC games instead of X1+PC games
Sounds legit

The future of Xbox is a Steambox without Steam? The future is bright indeed....