Originally posted by Ric it seems that a FF mirrorless is the wave of the future.
"Seems" is the operative word here. The biggest plus in my eyes is the ability, for those makers who see fit to allow for it, of using others' lenses on your camera (hello, LBA).
Originally posted by Ric So why not stick with a perfectly good APS-C and wait for pentax to come out with the FF mirrorless.
Because that may never happen, and if it does there isn't even the hint of a timeline for it. Pentax's APS-C mirrorless (the K-01) wasn't exactly a barn-burner; Ricoh Imaging may be once-bitten, twice shy on that one. I think you're likely to see at least two full-frame DSLR bodies (high end or low end or FF and FF Mark II) before you see a mirrorless FF with Pentax on it.
One of the reasons I'm not keen on mirrorless is that in order to see exactly what you're going to get, the sensor must always be "hot" and the EVF or the screen back always active, which eats batteries. There's no quiet mode, where you can just zoom, compose/prefocus and wait at leisure, then wake the camera up with half a shutter press before taking the shot. Better power storage and more economical (and faster-responding) EVFs might fix that problem, which would be good from my perspective because I wouldn't at all mind a retro-style full-frame DSLR in a Pentax MX-sized body, possibly even with Pentax MX-style control knobs and a decrippled K mount for working with film-era aperture rings.