So, we've been successful in getting a dash to boot into a Control Panel of our creation, activating it on the chumby.com site, and playing apps from channels in existing accounts.
There's still a lot of work to do - disabling the middleware that relies on the soon-to-be-gone dash service, adding the device as a validly supported one, etc. However, my guess is that we'll be in very good shape before the official shutdown.
The very, very good news is that we've been able to do this without having to modify the Sony firmware - this will work with a stock device that's running the latest (1.7.1526) Sony firmware release. Should Sony issue another firmware release before the July deadline (which is highly unlikely under the circumstances) please don't install it if you want to carry the device forward with chumby.
In the worst case, you might have to run the device with a USB dongle inserted at all times - you should be able to find one that's small enough to fit with the panel closed - and we're actively working towards a method of doing a one-time install of some software on the device and not needing the dongle from then on.
In any case, the bottom line is that Blue Octy should be able to provide most chumby services to the dash.