Not concerned with this at all. It's the right move. A turbo 4 isn't a bad thing at all. I have been to dyno events where properly tweaked Solstices and sky's put out almost as much HP to the wheels as a stock 5th gen SS and with little modifying.
They will still offer V8's for those like me who wouldn't have it any other way and I suspect they might even offer a V6 at least for the first year to test the waters. I believe that after they see where the take rates go the V6 will fade or they will turbo that and push the V8 up into "ZL1" price brackets only. Of course it all depends on what sells and who's willing to pay for it. $$$ will decide as people make the choices for GM with their wallets.
At any rate I suspect we'll end up with a 6th gen Camaro that most of us will love, some will hate, and others will love but complain about them not doing ____X____.