upgrade or wait

I have a D40x and I am thinking of upgrading to the D5000 or the D90. The main things I am looking for a better high iso performance, live view and video. I dont plan on using the video function a lot but I think it will be nice to play around with. I have friend that wants to buy my D40x for around $200 to $250 so upgrading to the D5000 would only cost me about $300. (D5000 is $550 on Amazon body only) So my question is should I pull the trigger on the D5000, save a little more for the D90 or just wait for the next big thing to come along? My current lenses are the 18-200 VR and a 35mm 1.8. Thanks.