I have a feeling the devs won't be taking half measures with the next update. They're no doubt aware that 10-15 new levels won't make much diff to serious players. My tip (based on nothing but lack of sleep and a vivid imagination) is for 35 new levels to round it out at a nice 150 (with more substantial xp gaps between). 35 new decorations and 35 new buildings (1 per level), along with the promised 6th farm (min 250mill cost) will give us all plenty to play for (and with) for some weeks to come