Just because they haven't yet reached the 'extinguish' stage of their strategy (and possibly never will), it doesn't mean that isn't the intended outcome. And going by their past behaviour; history would suggest that is their eventual end goal.
As for whether ASP.NET on Linux will ever attract many new developers; I must admit that I'm inclined to agree with you.
They may attract some Java developers, but I don't think it has much appeal outside their own ecosystem.