@sir82 no its not 100% true cause the same official letter speaks about building entirely new Kingdom Halls and refurbish a lot of them too. So what is happening is abandoning old/rented buildings and build new ones.
More and more you see that they build new Halls with more than one auditorium or make with 2 or 3 congregations use of one audiorium on different days and times. That only makes sense in areas with a good number of congregations.
It has nothing to do with decline or hollowing out, but is all about ownership, cost reduction and efficiency.