Google's removal of SD card has nothing to do with making device useless ever few years. It has everything to do with their cloud strategy. Google wants everything in the cloud. If your information is in the cloud, they can possible get access to it to better understand you so they can target more relevant ads. If your information is on the cloud, you will also have to spend more time online. That's why google devices, phones, tablet, chromebooks don't have removeable storage.
I would never buy a new phone unless it has an SD slot or perhaps 64GB of storage. How useful is the cloud when you're literally above a cloud in a plane? That's mostly when I use my phone for music playback.
You can use Google Music. It will cache content while on wifi for playback when you have no connectivity. This is done somewhat intelligently and you can also explicitly request content be downloaded.
