I also recently had a look at Sony's FF cameras and was quite impressed. I spent some time looking for reviews and oppinions, here's are two I found useful:
Of course, the reason why this guy included Sony in the big player league, and Pentax not, is his own opinion, and is valid for professionals.
Previously I never considered Sony as a choice, as I don't trust the brand (generally, not only for photo equipment). But I have to agree they made a smart move (as did Fuji a couple of years ago, imo), and they certainly had the muscle to do it. They might very well to be the leader in FF mirrorless, at least for some years. Looking back we can't dismiss the fact that they tried to innovate (I'm thinking of their SLT line), as did Fuji for that matter, and you we have to give them credit for that. They are trying hard. Time will tell if it will work out for them and reach a critical mass of professionals which will make the switch. Samsung tried hard as well in the mobile business, had a lot of failed projects, and look where they are now. I see no reason why Sony should not become the new Canon or Nikon. Dismissing them with arguments like "they are a consumer electronics company" or "they have no history in making lenses or cameras" seems silly. On the other hand they also made some bad decisions in the past which effectively canceled the potential of some technologies. Just look at their smartphone business, especially during the Sony Erricsson era, or the minidisc.
It would seem like the DSLRs don't have a bright future. They won't go away, for sure, but it will affect R&D and likely also the prices. I wanted to try out a rangefinder some time ago, but stay digital, and there was no option for me. Even second hand Leica's are way out my reach.It will be a sad day when this happens to DSLRs. Pentax has stated they will further invest in DSLR and that's great. For me, I just hope they will find a way to make K-1 (more) portable, or maybe an APS-C which is so close to FF that it doesn't matter anymore. I know, you can't beat physics, there will always be differences, but a super sensor with incredible dynamic range and/or low noise would leave FF with so few advantages that the decision might shift from APS-C vs FF to APS-C to medium format.
I shot only DSLRs until now, and I think I'll miss the OVF once I make the switch. It's the biggest concern for me right now. Probably the same way Rangefinder fans relate to DSLRs . That's of course not the case for the kids out there which grew with Smartphones and Digital point-and-shoot, and are perfectly comfortable with the EVF. Maybe that's one of the reasons for this big shift to mirrorless.