This is just a small compilation of things that are less known about 7.2, because I got tired of people being surprised every time I bring them up.
1) Tomb of Sargeras raid will come after another patch, most likely 7.2.5. Source: https://youtu.be/kpLwCPBFffk?t=2252 We can expect larger class changes and class balance done in this patch, as well as last minute item changes (set bonuses, trinkets, stat allocation), similar to how it was in Nighthold and 7.1.5.
2) You get at least a 1% dmg increase right away, if you have at least 36 traits. Old 54 = +14.5% dmg, new 36 = +15.5% dmg. This means that if your alts have 36 now, they will be even stronger than as if they had 54 now. Aside from this, if you are currently at 54, you will have 3 more points to spend, it's up to you if you choose to go for the new 4/4 trait for your spec or if you choose to add additional point to your old 3/4 traits.
3) You get AK 26 from completing a bunch of quests on the Broken Shore. This AK increases your AP gained by 4 times compared to AK 25. After that, each AK requires 500 resources and 5 days again and increases AP gained by 30% (so you get 30% more than last 5 days every 5 days). 37th trait now costs 10 million AP and then each trait is also 30% more expensive than the one before. This is a much more exponential growth compared to old trait costs, but as you can see, AK is designed to make you keep up with the growth.
4) There will be 3 new mythic plus options: Lower Kara, Upper Kara and Cathedral of Eternal Night. So far, I'm not sure anyone knows exactly how Kara m+ looks, as it's closed on PTR and I haven't been able to find any footage from earlier builds (if it was even open at any time).
5) Difficulty of mythic dungeons is increased by 30%, or at least the health of enemies currently is on PTR. As this is the base used to calculate the damage and health of all mythic+ enemies, that means that all m+ will be tuned higher as well. Here is a simple chart:
As you can see, new mythic dungeons are slightly harder than current +4 dungeons. Current +15 is slightly harder than new +11, etc. But since Tyrannical and Fortified were also nerfed, the difficulty of keys above +10 will change completely.
6) Rewards from dungeons are increased. Heroic dungeons now reward 845 base item level, mythic dungeons reward base item level of 865. EDIT: Updated rewards have been posted by Blizzard. Reward goes up every 2 levels of mythic+, up to a cap of 890 in mythic+10, see more on https://us.battle.net/forums/en/wow/topic/20753795211
7) Item level cap is staying at 925 for the time being. It will most likely increase with ToS release again. Newly dropped legendaries are still 940, even though dungeon journal showed them at 970 a few builds ago - again, we will probably get to upgrade them once ToS comes.
That's it for my simple list of changes that I found people were often not aware of. If you think I missed something important that was not covered by blues before, feel free to post it.