Unfortunately I think computer books in general are on the decline. It's just very hard for that medium to keep up with the pace of change. This saddens me because it is by far my preferred method of learning new technology, but it certainly seems like video content is winning out over books. YouTube, Udemy, WWDC videos, and similar seem to be the best way to get up to date information now.

There are still some high quality publishers out there, but I fear that we're coming to the end of an era. In addition to the ones you mentioned Manning and No Starch Press produce consistently excellent books as well.