Now or later?

I just saw this Dallas Morning News article about the the dilemma American Airlines (and I'm sure other airlines as well) is currently working through about whether to replace its old planes with newer more efficient models or hold out a few more years for the next generation of efficiency.

The upcoming Boeing 787 (and the Airbus competitor, the A350XWB) is "a smaller wide-body aircraft that uses improved engines and lighter-weight composite material to save fuel." However, there's not yet a production timetable, which means that airlines such as American are just kind of dragging their feet, but with the second-oldest fleet among the big U.S. domestic carriers, decisions will have to be made soon.

The get-it-now-or-wait-for-higher-efficiency-models question isn't limited to large companies. I've been struggling with the same question whenever I think about bigger-ticket items such as solar panels. I've heard that the technology will improve by leaps and bounds in the next half decade.

If I started using solar panels now, I would be supporting the industry and I would be able to turn some of that sunshine that I can see out my window right now into energy. But then in a few years I'd be stuck with a relatively inefficient system and if I upgraded, would be creating more waste, and complicated waste at that. What to do, what to do?