This has basically already occurred IIRC - the entire bitcoin blockchain is now too massive for most people to entirely download and authenticate; most people rely on exchanges, etc to do it for them.
The initial sync from block 0 can take a while, but after having an almost synced copy, getting it up to date is fast
I remember thinking "this will never work" after reading the bitcoin whitepaper, i assumed that at some point only supernodes would exist. We might be getting there, be we are not there yet, and definitely moving at a slower pace than my initial prediction. Holding 400-500 GB is still very attainable today at a small cost