'Curious: When does the Sony DSLR line no longer qualify as "alt"?'
What heresy, how could you suggest such a thing? Sony is just a passing 'alt' nimbus cloud, momentarily obscuring the magnificence of the Canikon universe. Next week normality will return you can be assured, and business as usual will be resumed.
I remember a lot of people here saying Sony would not stay in the DLSR business, they just make low end junk lol, and it was all just rumours. I found that just bizarre. That's the thing with talk shops, they get insular, become an echo chamber and don't notice changes until it's too late. Standard elite behaviour, other stuff does not exist, until it does when reality bites.
But if you want to see what may happen with a dedicated Sony forum, go visit the Canon forum, it is an illuminating experience, almost a parallel universe - though being outsiders, Sony users may be a bit different. Maybe it's best this way after all...