The only rewards going away with July 23rd are the 0.1% M+ Title Reward, and rated PVP rewards. It is only the competitive aspect of the season ending.
KSM, KSH and the teleports from +10s are still obtainable for M+. For raids, all raids will be awakened and you’ll still be able to obtain the mount from clearing all 3 on normal, the title from clearing all 3 on heroic, and the teleports from clearing all 3 on mythic.
These will be obtainable until the expansion launches. Blizzard hasn’t exactly clarified which date that will be due to early access so I’m going to say plan for August 20th as the date in which the rest become unobtainable. Thats the Tuesday before Early Access and Expansion Launch.