I'd say look at the lenses you've already got before second-guessing what you'll need after a new camera arrives. I don't believe either 30mm or 50mm would be wide enough for me to do landscapes.
Once you've worked out what focal length is missing for the new sensor size, then it's not too difficult to pick a lens that suits.
me, I generally have a 16-35, 24-70, or 70-200 mounted. The 50mm f/1.8 I've loaned out as I never use it...
some fairly old canon camera stuff, canon lenses, Manfrotto "thingy", and an M5, also an M6 that has had a 720nm filter bolted onto the sensor:
TF posting: here 