I believe it, especially with that "Exclusive! World premiere!" voice booming at the start of every trailer. I've seen MS conferences back then, and they pride themselves announcing games first than Sony with exclusivity deals.

I wouldn't be surprised if Microsoft itself was behind this "leak".

Maybe to lower people's expectations?

This is very much their style...

It's 2018, I assume people know MS is supporting both of their platforms. Sorry

I'd be curious to know which ones you're expecting to be on steam

Halo: Genesis is quite plausible and I would love it! I hope theu take their time with Halo 6 and make it even greater than Halo 5, especially improve the SP storyline.

Fake. 343i said that Halo would have got a new trilogy plus the 5 has a completely open ending so i can't see how the will work on a reboot. They already lost part of the community starting with the fourth chapter, if they do not finish the new trilogy they will lose another part of the community, and credibility.
I can't see happening third party games on gamepass at launch and even Microsoft pay for another timed console exclusive such as Splinter cell. For the rest, pretty delusional list in my opinion.

If it was a real leaked of the Microsoft press E3 2018 conference it would be peppered with ID@Xbox games.

More fake news based on known information. All the games releasing on the Xbox gamepass will be huge if true.

Forza 4, Screamride 2, Last Night, Shadow of the Tomb Raider, Banjo Anniversary & More. Xbox gamepass is getting bigger and bigger and if Sony doesn't respond it will start getting major momentum. Xbox gamepass combine with sub $199.99 Xbox One S is going to be a big deal.

I enjoyed Halo Wars 2, very underrated game. Its main gripe I believe is the restrictive game play which was introduced in Halo Wars 1. Halo Wars 2 offers a great backstory for the Banished and set-ups the flood perfectly. Also its cinematics are top of its class and well worth watching just for the CGI scenes. Reminds me of the best of the Halo days. 

I recommend trying it out at least before the next big Halo release.

As for Halo Genesis, I really wish it goes back to the dark days like Halo Reach was, where its more a pre-qual and a impossible mission. Strangely enough my 2 favourite Halo experiences came from Halo Reach and Halo ODST. I just loved the dark story plots in Halo games. Halo Wars 2 is similar with its plot, well with the flood introduction anyway.

So you expect several of those games to be on Steam and only named 3 which will make it to Steam by assumption?

If you haven't notices MS's tactics, they only release the games that don't sell well on Steam. None of Xbox's big games have crossed to Steam apart from Killer Instinct which is a launch title game. There latest releases like AoE RM and Sea Of Thieves have remained Win10/Xbox Exclusives. I also predict Ori 2 will remain a win10/Xbox exclusive however I see State of Decay 2 arriving to Steam. 

Halo certainly needs a reboot to bring everything back to basics instead of the current mess.
But I doubt that will occur until Halo 6 has been concluded.