I used to use the 80-400mm quite a lot, even for sports. I always found it sharp enough for film or lower MP cameras. It's a good lens, although a little long in the tooth. In low light, it doesn't focus very well at all. I eventually sold it when I purchased the 200-400mm. One of these days, I'm sure Nikon will update with AF-S and nano coating. At that point, I'm positive it will be a stellar alternative. Seeing as you're saving, maybe one will be announced within your time frame.
One option, that I would recommend is to buy an AF-S 300mm f/4 and use with a 1.4TC. This gives you the flexibility and relative lightweight of a telephoto plus the added reach when you need it. The 1.4TC only costs you 1 stop of light and is sharper when attached to the 300mm than the 80-400mm is at 400mm.