When you say you're 'doing weddings, portraits and wildlife photography' I assume you mean professionally?
The question 'to upgrade or not to upgrade' confronts us all at one time or another, and the answer can really only come from you. If you're like me, you bought your current DSLR because - at the time - it suited your needs. Technology has evolved since but that doesn't necessarily mean you need to invest thousands of pounds in new gear if you're happy with your camera right now.
I've had many happy years shooting with my D70, but - particularly as I handle the latest cameras on a regular basis for DP - I find myself becoming a little frustrated when using my own camera. In essence, I've 'outgrown' my current DSLR, and feel an upgrade is well overdue. I'm not upgrading with a view to improving my photography - as that can only come from the photographer. I'm upgrading because my style of shooting has changed and my camera doesn't fit with that style anymore. (Plus, my 'new camera fund' piggy bank is finally full!)
If you've genuinely outgrown your D80, a D300 or D3 are both outstanding cameras, although obviously a D3 would set you back considerably more than the former, so it's worth considering what you actually do with your images, to see whether you can justify such a purchase.
If you still want to upgrade - go to a shop, handle both cameras, take a memory card and bring your test shots home to scrutinise - make sure you're completely happy with your decision before making a purchase.
Whatever you decide - keep enjoying your photography!