If you aren't in a great rush, if I were in your shoes I would wait until the release of the new one: you might as well see if it's worth it and you can sit back smugly knowing that you have the latest and greatest for at least the next 10 minutes! 
One thought for you though, whichever you decide, think about a machine from the Apple refurb store. I got mine there with a couple of 100 quid knocked off the price and it has been terrific. On reflection it's arguably better than just getting a new one as some poor sod has already found out where it was broken and had it fixed for you. And even if you choose the new one, I'd be surprised if you had to wait much longer beyond the release for them to turn up in the refurb store.
One thought for you though, whichever you decide, think about a machine from the Apple refurb store. I got mine there with a couple of 100 quid knocked off the price and it has been terrific. On reflection it's arguably better than just getting a new one as some poor sod has already found out where it was broken and had it fixed for you. And even if you choose the new one, I'd be surprised if you had to wait much longer beyond the release for them to turn up in the refurb store.