I too am finding it quite slow paced. For me in Mexico there is the prospect of being able to open more bases in future as demand grows, but for those who have already reached their max number of bases and covered most of the demand now all they're really going to have to do for the next year is add the odd flight when demand rises and handle fleet group transitions. I can see people getting bored.
On the flip side, I love the idea of planning out how my airline is going to look in half a century's time! Working through the different fleet transitions I'll need, and how to time them so I'm not juggling too many fleet groups etc. That is a lot of fun.
So for me I think the solution for future worlds is:
(a) introduce an auto-replace tool that will make fleet transitions easier, as requested in this thread http://www.airwaysim.com/forum/index.php/topic,49069.0.html
(b) reduce the default ticket prices by say 15% so that big airlines can still grow up, but will take more years of gameworld time
And then when the above things are in place:
(c) radically speed up the gameworld to be 12 minutes / game day.
With 12 minute game days, a year will take 3 real life days and a decade a real life month. However, the pace shouldn't seem impossibly fast because it will take airlines longer to build up decent savings - so if they are currently ordering 2 new aircraft per real life day, they might still be getting 2 aircraft per real life day, it's just that twice the amount of time will have passed in the gameworld. The main difficulty with this is fleet transitions, hence (a) above. Other timings might need to be re-visited too; perhaps 5 years for a new base?
On this basis, a 1950-2030 gameworld would take 8 months, so if you had 3 running concurrently you could have a new one starting every 2.5 - 3 months.