I don't think a lot of people are going to buy hardware specifically for running Bitcoin, why spend $150 if you can just run a light client even on your phone instead?
Either they do, or they don't.
But the same applies to the current state too.
Why are people running a full node nowadays if they can run a light client on their phone ?
This has nothing to do with storage.
And I know there are always Bitcoin enthusiasts who own multiple full node machines, but they are a minority, most people run nodes if they can spare resources on the machines that were bought for other purposes.
A lot of people already own 1 TB HDDs.
With the increasing popularity of SSDs and their decreasing price.. what will the 1TB HDD's be used of in 5 years ? They won't be worth anything. Might as well use them to store blockchain data if you don't want to throw it away or store them on one of your big future-SSDs.
It's true that the storage is increasing, but the demand for it also increases - programs weight more and more, Bitcoin blockchain is growing.
The 'demand' does not increase at that pace. By far not.
20 years ago you could barely store the operating system on an optical drive.
Now you get 8TB storage for a fraction(!) of the price. And those 8TB are way more than needed for 'programs' nowadays.
Storage really isn't any issue at all.
People who are running a full node today, won't have a problem running one in 20 years. At least not storage-wise.