I have to admit that my understanding that BS7 is under water are references to that effect by other hams.
+ Actual evidence - pictures of the "operating rocks" at high tide in 1994 and data on changes in sea level since then - would indicate that the "operating rocks" are still above water at high tide.
But even if it was not currently under water, is it likely to become activated?
+ Throughout the entire history of the DXCC award program, "likely to become activated" has never been a consideration for DXCC entities, much less a requirement. DXers who pursue "Top of the Honor Roll" do so with no assurance that every DXCC entity will be activated during their lifetimes; the willingness to pursue it anyway is what sets them apart.
+ If you find this uncertainty uncomfortable, that's fine. There are plenty of DXing awards for you to pursue where the absence of activation isn't problematic.