Why don't you buy a used 70-200 f/4 on KEH now and a mid-grade monopod and quick release right now. That will suffice for your trip. In the short term, you'll have the focal length. You'll also find out if you need a faster lens in that focal length. If you do, you'll likely be able to sell the f/4 on ebay for what you paid for it (possibly more).





Keep in mind, I own the 70-200 f/2.8 IS and it hasn't seen the light of day in almost 2 months...