I am also a member of the World Design Team, got that same email.
The way that I read it was that 7e7 variants
will still be flying up to a hundred years from now. That's not at all illogical to think of.
The B-52 example is a good one. However in this context we're looking at something different.
Try this on for size:
In about 15 years Boeing may or may not start looking at a replacement for the 737NG. By then the 737NG will be a 20 year old design, and the 7e7 will likely be enjoying good success in the long-haul, medium-high capacity markets. The SR
version with 300 pax will probably have just started getting popular after a very slow start in Asia. And Boeing will either be looking at making a 7e7 narrowbody with 200 pax, or will have already done so.
When the 737NG's life nears it's end. Boeing will likely use the 7e7 design to create a replacement. If a 200 pax narrowbody 7e7 will have already been produced, Boeing might shorten it. If not, Boeing might create one with the ability to be stretched....exactly like the 737NG but looks like the 7e7.
The 737 in all it's variants has enjoyed a production life of almost 40 years, and we can reasonably expect 15-20 more years for production. Therefore it's not impossible to expect:
7e7 base: Production 2008-2028
7e7LR: Production from 2008-2028
7e7SR: Production from 2009-2024
7e7 narrowbody first generation: 2017-2040
7e7 narrowbody NG
The last narrowbody 7e7 would end up being about 40 years old by the time the new century dawned.
As can be clearly seen, there are 707s older than 40 years old still flying in some remote regions of the world. This is not an impossiblity for the 7e7 to also achieve in some form or another.
I think Boeing is going to milk the 7e7 for as much as it can. I dont doubt at all that the 7e7 will eventually be spread to cover all product lines. This makes for a VERY boring future...but...an efficient one.