Why a 7D? You can shoot HD video with the 550d/600d/60d, all of which are cheaper.
i picked one up today and had a play... its a massive step up from my 500d, so much so i genuinely didnt know where to begin. It felt like a whole new system. Also, when holding it i felt like a man.



If you have a D40 then a Nikon D7000 would make an excellent upgrade and everything will feel familiar.
The D7000 has a mag-alloy body, class leading sensor, excellent auto-focus and metering and comparable video to the 7D.
This will save you a couple of hundred and if you are used to your D40 you wont need to re-learn any reversed zoom rings etc.
I think this answers lots of questions
A little off topic, but you do know the d300s is a dx sensor, right? Unless the D400 (or whatever it'll be called) is a full-frame (doubt it, given the D700's placement, there isn't much more to trim off, and I'd be disappointed if Nikon stopped their pro crop sensors).I'd recommend trying one, I've been very taken with it the couple of times I've had a chance to shoot with it. If I wasn't set on moving to full frame I'd be very very tempted rather than waiting for the D300s upgrade.