when one owns 3 28B's and is looking for a surround amp, I think its a worthy question.
how long before we can expect similar Bryston products?
Absolutely. A valid question. I've maybe asked James 3 times in the last 5 months and one of the reviewers from 6Moons asked a couple weeks back

However, for a 'surround amp', I would imagine any of the other SST series would do fine. I have a 6BSST now and it almost breaks my heart to think that an amp of that quality will be powering my back speakers soon (almost)

But, a set of 7BSSTs or a 14BSST (hopefully with the benefits of any tweaks from the subtle design changes in the 288BSST) is on the very short list of new amplifiers that I will be buying in a few months to power my fronts, so.....to the back speakers the 6B will go.
I would think a 3BSST would be more than enough for rears, and as James as said earlier, the design tweaks in the SST series that may trickle down will likely not be beneficial to the smaller amps, maybe only the bigger amps with more output devices, like the 600 watters.
Keith