My answer to 'wait?' questions is always a question- can you wait? If you can wait then you might as well.
If you need something now, buy now. If it were my choice and I needed something now I'd choose the brand/model I like and that meets my budget. The 590 is really just an overclocked 580 isn't it? So I wouldn't be willing to pay a premium for one. If a 580 isn't enough for your needs that means you need to choose a card in a higher class, not the same card but overclocked.