I don't think there was malice involved. Sonos seems like a company that has a very tough time making money, and since they IPO'd two years ago they are "responsible" to shareholders now (their stock opened at 15 and as of Oct 2 it was 15 -- could be worse!). Bricking old products would give a profit boost if everyone said ok and bought new products, but they underestimated the backlash.
It's the same reason their client sucks -- it will cost a lot of money to make native apps that take advantage of the respective eco-systems. The client suffices for most people so why bother?
That said, I'll go back to being pissed if they release new hardware I want and get rid of the 30% discount.