First of all, I don't think much of what we see around us now will survive to reach the future. All the plastic containers and ads, all the iphones and books...all that stuff will be incinerated by successors who just want to get rid of the clutter. One thing that might survive, oddly enough, is hard wood furniture because old growth wood will become a luxury item as forests disappear. If you have a message to convey to the future you might consider carving it on the bottom of your wooden dining room table if you have a nice one.
I'm glad we have a Library of Congress and a Smithsonian but these institutions are vulnerable to fire and war, and to the apathy of the public if the culture no longer values what's in them. My guess is that most of what's in those institutions is sitting in Bekins Storage-type warehouses in the area around Washington D.C. A fire in a single Maryland Bekins could wipe out a whole chunk of American history that's preserved there.
Then too, what the Smithsonian decides to keep is problematic. The history of a powerful lobby like feminism might be secure unless America converts to Islam, but less powerful interests will go undocumented. We only have pictures of some of the great jazz musicians because a single individual decided to photograph them. The Smithsonian never photographed Spumco. The Savoy Ballroom and the Jitterbug weren't much covered by Smithsonian photographers. The dancing in Black clubs today is underdocumented in pictures.
My prediction for the future is that it will ransack the past for inspiration in every cultural area. If you were to step out of a time machine in the future you'd see buildings benefiting from the latest technology to be sure, but you'd also see recreations of Fort Apache, old pagodas, the Parthenon and 50s "Googie" diners. The 20th Century will be well represented because epochs that creative are few and far between and the future will want to understand how we did it.
My guess is that the future will delight in imagining how we lived in our time. They won't hold our limited technology against us, they'll envy us in some respects. I picture levitating brains of the far future doing cosplay recreations of what it was like to be a cartoonist at Spumco. Wearing all wrong interpretations of the clothing of our time, they'll meet in clubhouses and try to recreate a typical morning at Spumco of the 1990s:
BRAIN #1: "Greetings Jun Krid-faal-lucy (John Kricfalusi)!"
BRAIN #2: Greetings "Veen-send Wahl-lair (Vincent Waller)! Let us have a Gog Session (a gag session)!"
The brains, dragging faux blue jeans from their undercarriage and wearing knitted Superfly hats, levitate to a room with a conference table.
BRAIN #1: "Okay, I have a gog that is quite humorous: The Ren dog gets into a sanitizing water container and furts (farts). Ha-ha-ha-ha."
BRAIN #2: "Er...what is a furt?"
BRAIN#1: "Um...I don't know, but a methane bubble is created."
BRAIN #2: "A bubble? Hmmmm. Let us have
two bubbles to make it
twice as good! Ha-ha-ha-ha."
And so on........