With the change in 0.17.51 the aliens are now attacking again. Not quite as strongly as they did before, but they are definately showing their opinion about my presence

With update 0.17.49 we saw some changes in the way alien attacks are orchestrated:
Reduced the UPS impact of a large number of biters trying to pathfind. ( 71865 )

In my game it now looks like the aliens have given up. With 0.17.48, I had regular attacks on my base that looked like this:
Biter ...