She has high hopes for science and Instagram.
“Dear Kim, When you read this, you'll be ten years older in the year 2025. I hope this is where you are."
So she's either hoping to still be alive, or she is writing a warning to a future in which time travel has been invented, and she is caught in alternate looping realities. This is indeed a dark fate for future Kim.
"When it comes to how you'll feel about your body, remember to be kind to yourself and enjoy how you look now because you're not getting any younger."
Kim is talking about the theoretical effects of time travel. Surfing the fabric of spacetime can have devastating impacts on complexion and neurological function.
"I trust that you will still be the queen of contouring."
It's pretty easy to ensure the continued success of your career and subsequent product line endorsements when you can travel back in time to manipulate supply and demand.
"May science invent a mysterious and delicious green juice to keep you tan forever."
This is Kim's most unsubtle hint about what the future holds: there is a green juice that keeps you tan forever.
“If you haven't broken the hundred billion mark on Instagram followers I'll be very disappointed in you."
Clearly Kim is manipulating the future, because no app or social network will be popular ten years in the future. Luckily Instagram is in her favor. Let's just hope Kim doesn't meddle with world affairs or the fate of all humanity.