On the subject of modularity, with the waterproofing and USBC, we are seeing the phone/tablet losing hardware features and becoming a "pure" computer these days. I would argue that with gadget/appliance makers putting in Bluetooth/WiFi connection and integrate with a phone app, it's a way of making the phone "modular".

Instead of buying an expensive modular camera part for my modular phone, buy a mirrorless camera with Bluetooth and now that can send photos to any phones

And if someone really want high quality analogue audio, instead of the headphone jack in the phone, they can buy a DAC that's dedicated to doing just that.

Outside of stuff like machine learning or graphics processing, IMO a modern phone don't really need to be updated for a while. With stuff like cloud gaming and other cloud based services being more common place, it's likely that we only need a simple device that's capable of streaming content.

Edit, just saw your comment about laptops. I hold similar views there, I think they are getting to a size that more or less plateaued, there's not much to gain to make them even thinner. Yet I also don't think they need to be modular anymore, when USBC gives you all the expandability. Webcam, WiFi chip, display, even graphics card, plug it into the USBC port and it's done. While any more involved processing would be done on the cloud.