From personal experience when the gtx780 just came out I would sit and watch during the time if more stock would come and probably a couple times a week most brands will have more and more in stock...
I would assume that would work the same for the 280x I would just wait and keep checking every time your not doing something.
Get what you want especially something that much and you have to live with it for so long... You will only have to wait a couple of days and if you are on it you can get one. Trust me I did and I never regretted my 780 love it to bits!