When British Airways do cancel, you have a good (IMO) chance of winning compensation in the UK Small Claims court process *IF* you believed this was a valid fare and not a mistake. If you believed it to be a mistake, then you've no chance, but otherwise you can reasonably rebook a full cost business or first ticket and claim that back via Money Claim.
British will almost certainly cancel these as they know most people don't bother (same goes for their general poor treatment of customers overall). I firmly believe they simply don't care any more - current management does whatever they like in the interest of cost savings regardless of what's allowable anymore.
If you don't rebook any equivalent flight (with a new ticket cash or award), you'll have trouble claiming much from them as you won't be able to show damages. If you do this in US Small Claims, I've no idea.
There are lots of folks with similar cases out there, so when it comes time I'm sure you'll find helpful advice. But the crux of the argument is your own intent when booking and to pursue this in court you need to honestly say to a judge you believed this to be a flash sale or otherwise a valid fare and not in error.
Not a lawyer, not legal advice, YMMV and such.
Last edited by balover_69; Oct 3, 2017 at 3:56 am