From what I read elsewhere... the "practice strikes" and strike threats are posturing used by the Delta union to get management to talk to them. Apparently it's not working yet. I suppose now that the lockers being cleared today will make management at Delta nervous enough to end the impasse. If the pilots do strike then there is little doubt that Delta will be finished as passengers take their business elsewhere and those inconvenienced will demand compensation at virtually every airport Delta operates out of.
I'm begining to understand that airline pilots do these sorts of things to maintain a level of fear and leverage against management so that they are not treated like ordinary employees, but as the backbones of the companies which they serve. But in this case I would have to strongly disagree with the Delta union if they do indeed end up striking. Maintaining leverage is one thing, but pretty much ending the company you work for is an entirely different animal.
I am almost sure that if everyone at Delta... especially, managment have been reading their history books they will come back to the table and arrange at least a short term solution with the pilots so that they don't go the way of Eastern Airlines.