The KP will be a massive step up from your K-r, and will serve you very well for landscapes. The resolution increase will surprise you, and the articulated screen is very useful for low angle shots in the field. Pixel shift will also be a boon.
Your existing lenses, stopped down as is usual for landscape work, should be more than adequate for starters. For a bit more width, flare resistance and starbursts you might want to add a DA 15/4.0 Limited.
Full frame is great, but if you intend to hike deep into the hills you will notice the difference in your carry
Some KP landscapes:
Skagway, Alaska. DA*11-18
Skagway again. DA10-17
Lemaire Channel, Antarctica. DFA28-105
Lake Como, Italy. DA21
Siena, Italy. DA15
Rome, Italy. OK, it's not really a landscape
FA43