The game is still in development, but the goal is to have a space program that you have to manage. Prices for different components has already been shown in-game but they don't mean anything yet. More planets seems like it'll be a no-brainer but they're not that far yet.
Here are the planned features for the game:
http://kerbalspaceprogram.com/~kerbalsp/wiki/index.php?title=Planned_featuresAbort Sequence for emergencies.
EVA's
Docking
Internal camera views
Crew Tasks: Have the crew take charge of the ship
Astronaut Complex: Hire and train kerbonauts
Research and Development: Discover and improve parts (from tech tree)
Part recover
Runway to land on or launch from
Spaceplane hangar: A secondary VAB that allows horizontal (belly-down) construction
Mission Control Room: Creat flight plans on missions and challenges
Observatory: Discover new celestial bodies to vist
Exploded View: A schematic visualization of the ship, allowing for greater control over ship functionality.
Tweakables: Context menu when right-clicking a part
Stack extensions: Fairings and solid-booster fuel plugs
Side-mounts: Drop-tanks and cargo pods
Spacecraft Stats: Total weight, Loaded fuel (per stage), Thrust (per stage)
Wind/Turbulence conditions
Reentry heat
Possibility of reentry heat weakening structural connections
Clouds, weather
Static particles (cloudlets)
Long-duration smoke trails
Fuel-dependent larger explosions
Asteroids
Other moons and planets
Matching launchpad scenery in flight
Cities and other geographic points of reference
Space Center Facilities can be destroyed by crash-landing onto them, and fixing then will cost
More and better sound effects
KSP Soundtrack
OSC Data Interface for connectivity with external applications
More complete SDK and documentation
Normal map support for part textures
More modding opportunities than just parts