Based on this FlyerTalk thread, it seems like one can get Silver status with British Airways just for getting the British Airways Visa Signature Card. Unlike the “Silver” status level at many other airlines, BAEC Silver is actually worth something. It even gets you lounge access when traveling domestically on a OneWorld carrier. There is a $75 annual fee for the card, but this is still an incredible deal for those doing any OneWorld flying.
I would wait before signing up as details are still unfolding, but this is something to monitor.
Update: It looks like this offer is targeted.