Now that Sony have announced the PS4 is getting an upgrade to HDR next week, will MS follow suit and allow all their fanbase the benefits or will they keep it as a selling point for the XB1 Slim?

i think they will

I feel as if they have to to be honest. It's not something anyone is talking about at the moment but I'm sure it's going to come up after the dust settles. If they don't there could be a backlash from existing fans ... maybe even 'meltdowns'!

I think if they can, they should.
And if they can, why havnt they already? was it all just a ploy to sell their Slim? when the orginal could have had it anyways?

We ll find out if they do manage to get it, for the original xbox one.

That's the main problem they have. They've used HDR as a selling point for the Slim and now find themselves in a awkward situation. If they don't then their insall base will be asking why and if they do Slim owners will be asking why it was advertised as a 'benefit' for buying the slim. That's why I said Sony just cut them off at the legs when they announced HDR for ALL PS4s. It's quite the chess move and one we'll see played out slowly over time.

If that happends its this all over again:

It will put MS in a bad light,...

No. Coming out of E3, the big selling point of the XB1S was HDR, not 4k. They need it to move consoles.

(Looking forward to the retconning that 4k and UBR were suddenly the defining features!)

I added a little more.

Indeed, this is going to be an interesting game to see played out.

Most likely not. The XBO S upped the performance 7% just for HDR. Sony has the headroom on their OG system to support it, most likely freed up from the OS. If you remember, when leaks were coming out about the PS4, it was stated Sony was being very careful with how much they reserved for the OS, reversing much more than they needed to.

If they wanted HDR on regular xbones it would be out by now because the S has it. I doubt they will launch it to non S owners.