Perhaps one should mention that Ansel Adams shot his famous image "Moonrise, Hernandez" with an 8x10 camera (i.e., the film size was 8"x10", and the crop factor would be 0.14x). Now, granted, a view camera allows lens/film movement (tilt) so you can also use the Scheimpflug principal to increase the DoF, but generally speaking, no, shooting any currently common digital sensor format won't keep you from being able to adjust the aperture so you'll have sufficient DoF to cover a scene for landscape shooting. While a bigger sensor will decrease your DoF for the same framing and vantage point compared to your P&S camera, your P&S camera has a far smaller aperture range available. Most P&S cameras stop down to f/5.6 or f/8. Most dSLR/mirrorless lenses stop down to f/22. And Ansel Adams, well, there's a reason the group he participated in was called Group f/64. :)
Diffraction limit for micro four-thirds is theoretically f/5.6, but in practice, going up to f/11 doesn't pose any problem for me and I don't hesitate to use f/16 if I need to. I'm actually pretty happy shooting landscapes at f/8 or f/11 most of the time, without messing about with hyperfocal calculations.
See also: the "micro four-thirds images" thread on the fredmiranda "Alt. Gear" board.