I am currently on en72 and en86 and these are the differences I could find :
1) Heroes system. In 4th generation, I think inno is testing the system using the island quest. The true intention behind this is to generate coins for the heroes which is active in 5th gen.
2) Academy. 4th gen max 30, 5th gen max 36. City Festival and Olympic Games can still be held at level 30. There are good technologies at higher level, so level 31 and 34 cannot be ignored.
I'll update if I find more.
Not exactly true, Zancle had all the updates you talked about and it's 4th gen. In reality they are now just a chance to start the alphabet over/switch name systems. 1st gen stopped at update 1.26 for a long time(they did switch it after about 6 months or so to enable WW). 2nd gen were the first 2.0 worlds i believe. Since then the updates have been more on a server to server basis rather than "generation".
Sorry for the digression, back to the alliance.