I hope they will wait at least 6 months before releasing the next age, give us some time to upgrade CWA (without having to use too much crowns).
Concerning the lvl, currently I'm CW lvl 255 and I still have around 30% of the defense buildings which are Atomic (my farms, oil, road and caravans are still at very low level), so I think that a level requirement of 260 would be reasonable.
Also, the level requirement of 220 for CWA was a very good idea from Nexon and it was necessary, I'm sick of all this noob players rushing through the ages with gunpowder defenses and units ... Sometimes giving too much freedom to stupid people isn't a good idea, you have to fix some rules if you don't want people to make stupid choices.