It depends how much a few months with/without a reader is to you. From what I'm hearing, the general consensus is the nook 2 will be out between now and December. So, you could wait between less than a month to three months. Or, the general consensus could be wrong and the nook 2 won't come out this year (unlikely, but possible).
Usually, I would agree with neilmarr. However long you wait is that many more days/months without a reader. But, since it could be so soon that the new one comes out and also since the holidays are coming (which means deals are coming) you have two good reasons to wait. If I were buying one right now, I would wait. Also if I were you, I'd just set a limit though, like if it's not out by so-and-so (such as December) you're going to go ahead and buy one then anyway and not wait any longer.
Then, even if the nook 2 hasn't come out, you'll have holiday deals, hopefully on the nook and Sony. Especially watch out for Black Friday deals. It may take some work to get them, but they can be really good.
Of course, before then a good deal on the nook 1 or new Sony may come along and you may pounce. And if you're really itching to get one now, then just go for it. At the worst, you can always sell whatever you get now to get a better one later on.