I just don't see the point of buying 17.3 x 13mm system anymore.
I do, provided size/weight matters - it's still the best affordable compact system. As far as I can tell there are no pre-existing really small FF Sony or Minolta lenses, prime or zoom, and the new lenses announced for this system aren't small either; and as far as I can tell, there's no such thing as a small FF zoom of any focal length, period (is such a thing physically possible?). So, if you want to retain compactness, you're limited - barring unknown future developments - to whatever small third party lenses you can attach (assuming they work well via adapters - and given how fussy 36mp sensors seem to be (see comments by Roger Cicala et al.), that's quite an assumption).
What's more, Sony has shot itself - or its customers - in the foot by not providing what has hitherto been a major selling point of Sony dslrs: in-body image stabilization. Until now, any lens you attached to a Sony FF digital camera (or aps-c dslr) benefited from image stabilization; unsurprisingly, Sony's A-mount lenses don't have IS - they don't need it. That's all changed now, of course, so in situations where IS is needed, unless you add a third party lens with IS or wait and buy new Sony lenses with IS, you'll need to use a tripod (as a tip-off, Sony adds a tripod mount to the adapter you'll need to attach A-mount lenses); and if you're going to use a tripod, there goes the size advantage and then some.
If these cameras had IS and an A-mount, I would pre-order one too (I wouldn't care if that required them to be a bit bigger; for me, size is the least of the advantages of ditching the mirror). Instead, I'll wait and see if Sony makes a mirrorless FF A mount camera (at least one A mount camera will allegedly be announced early next year). Until then, my Canon FFs and Olympus m43 will do just nicely....