Hello Ewa!
It's such a open ended question & ultimately very difficult to answer as there is not one shoe fits all solution. Do newer devices need more storage? Generally yes, as technology advances, manufacturers add additional features & benefits which in turn take up more storage.
Generally speaking, the content that takes up the most storage space on any device is any media, music, videos, pictures & downloaded content through apps, like Netflix shows, Sky, Facebook, Snapchat are common examples. If you aren't keen on sending your pictures & videos to the cloud, then you could buy a SD card if your phone is compatible, or an external storage stick which you can plug into your phone, but I would definitely consider using the Cloud, its fantastic once you get it set up & working! To answer your final question, I wouldn't consider getting a phone with any less than 64GB of internal storage if you want to future proof yourself & your device.
I hope this helps.
