Boeing hit it out of the park with the 737.Why change it. Its mission has not changed and midsized carriers will continue to purchase this plane because of its versatility. Damn hard to beat. get that airburst?
The replacement for the 737 (or as some are calling it, the 737-1000) will be based on 787 technologies. It will be more fuel efficient which is the most important thing in this day and age.
Because time doesn't stand still. The Next Generation 737s are amazingly versatile aircraft, but Boeing still needs to be working on their successor(s), to beat Airbus to the punch. The A320 series are pretty good planes in and of themselves, but Boeing had a significant advantage over Airbus there in that they had an established customer base and they knew what the customer base wanted to see in that segment, hence the Next Generation 737s (the -600 through -900 series).
Boeing can't sit still. Working on the 737's heir apparent has to start now.
}:-)4
If it broke, don't fix it, if the 737 sells, and customers still want to but it, then why change ,, other than making it a full composite body like the 787, and put fuel efficient engines on the 737 ( Smaller version of the GenX engines ) and make it more commonality ( as in technical advances ) with the 787.
Simple matter. A plastic 737 will be cheaper to operate and maintain and more comfortable to passengers. Combine it the new engines being developed and you will have 737's flying to Europe, further lessening dependency on the outdate spoke hub system. In addition, the 737 interior is very cramped. The A320 is wider and much more comfortable.