And thats why he said "life cycle" and not "development cycle" - which means for me, the time passed after the MMO went live

After the same time (as in, after going live) XI had more endgame content, more zones, more cities and more classes(and a shitton of more skills) then XIV, as well as 4 level cap increases for jobs and crafting(50 to 65/70/75 and 60 to 80/90/100 in 3 patches over the course of 11 month close to CoP release. After CoP it stayed at 75 for 7 years, making gear obsolete with the first Abyssea release.
The only thing that made your char stronger was the merit system which kept you working on a class after 75, which i really miss here. But it would end the same as the BiS bullcrap people are worshipping like monks on lsd.

Going with your holy development cycle, XIV would not hit the same point until 2017 until 4.0 is released as that marks the last update of RoZ and 2 month after the release of CoP. If they keep the time between expansions the same as 2.0->3.0 then the release of sea would get close to the equivalent of Christmas 2018 in XIV.