Is your profile up to date? I looked at your list of lenses to get an idea of your gear.
I'd rate the D7000 only a small step up from the D90 - and would not suggest making that upgrade. A D400 might end up being a better choice and it has not been announced yet.
The D700 is going to produce similar files to your current D90, but the FX image will change your perspective. One of the biggest differences is a shallower apparent depth of field. To get the same image from the same distance, you will use a longer lens with FX - and that increases subject isolation. I think this is the biggest difference FX will make in your images since you seem to like using creative depth of field and subject isolation.
An FX body will mean big changes in your lenses. Most FX lenses can be used with any camera, but DX lenses are not your normal choice with an FX body. I'd probably start looking at lenses rather than a new camera body. Look for high quality FX lenses like the 70-200 f/2.8 and a macro lens like the 105 f/2.8. I'd go a bit slower on the 24-70 f/2.8 since that focal length is covered by your current gear - but a 24-70 is a staple in most top quality kits.
The D700 could be a better first step than a D800 since you don't have the lenses to get the most from a D800. Keep the D90, add a used D700, and add the lenses you need for an FX kit. The D800 is a spectacular camera. It has slightly better resolution than the D700, and large file size to get the most from your lenses. But the D800 will reveal any flaws and is somewhat demanding. Given the timing, the possible D600 might be a worthy consideration when it is released.
I would not be in any rush to upgrade the camera body. Focus on your lenses and technique. And keep in mind that Nat Geo legend Bob Krist used a D90 for almost everything published over the past few years.