I agree that it would be interesting to see how the GWs develop with the newer planes.
I don't know when it was decided that GWs run until 2030, but as we're now in 2016 and know pretty well which aircraft will be coming to the market in the next couple of years I think it is reasonable to play the GW until 2040 or even longer.
However I have noticed the number of players in the GW falling strongly and even those that do not officially leave the game do (to a large fraction) not spend time "playing".
Personally, I have not been spending too much time with my swiss airlines in GW1 because there's simply nothing to do anymore. Last thing I did was fill the void that those players left that quit the GW to play a "younger" GW.
The problem I see is that
1) It's more fun to build new airlines in new GWs - I saw a big drop in our alliance's members after each new GW opened
2) Big airlines in "old" GWs are so rich that if the player didn't really mess up there's absolutely no chance to get into the game (unless you go to boring countries with so little demand that no one has bothered)
Along these lines it would of course be necessary to introduce some more "fictional" action like airports closing and opening - even though theses are in general also planned a long time ahead - even if they not always take as long to "open" for good as in Germany ;-)
Also, some changes in demand, fuel prices etc would be nice to have so that it doesn't all run that smoothly.
Something like the world-wide crisis of 2008 is not modelled, only 2001 as far as I am concerned, even if it had big impact on aerial companies.