Well, this judge would decide that motion, so it seems like he's told them they would be wasting their time. The realistic options are (1) file for a say ASAP with an eye toward asking the court of appeals to grant the stay after this judge denies it, (2) keep litigating after the deal goes through, or (3) admit defeat. I'm no expert in #1 but I assume it is also very unlikely to work in time to stop the merger (otherwise I think the DOJ would have gone that route).

That leaves litigating after the merger goes through, or just giving up. Often the FTC or DOJ will chose not to keep litigating mergers if they lose in district court because even if they win later, they don't think they will be able to get a very effective remedy--the deal will have gone through and it won't be possible to put everything back to the way it was. (If you are an antitrust lawyer, you for some reason have to talk about this using the phrase "you can't unscramble the eggs.") But it does happen sometimes--Whole Foods/Wild Oats was a good example where, if I remember correctly, Whole Foods had to sell of some of the stores they purchased from Wild Oats years later after winning their merger case in district court but losing the appeal.