If there is evidence of an attack or even when an attack seems likely the best thing to do is simply not engage in transactions. The old part of the blockchain will be fine regardless.
We don't find credible the claim of an attack against private keys (see mathematical analysis posted here). Of course we could be wrong, but we will cross that bridge if and when we come to it. No one can guarantee zero risk, but we believe this risk is very low.
You don't need to personally back up your blockchain, if there is an kind of attack against it there will be an update that will recover it just as there was with the last attack, which was likely far more sophisticated in terms of technical knowledge required than anything BCX has in mind, but that is just my guess. It can't hurt though.
Don't panic (ever). Wait for further updates.
Thanks, are you recommending to refrain from any transactions even now, many hours before the alleged start time of the attack (or is there a time later today after which we should hold off)?
I have not made any specific recommendation other than what I said above, please use your best judgement. We will have another statement later.
Of course it could.
Any estimate of when we should expect "another statement later"? Before or after the alleged start time of the attack?
I don't have an estimate at this time
I don't have any information whatsoever about anything unusual happening at this time. As far as I can tell, everything is working perfectly. Hope that helps.