I don't think the blockchain size will become an actual problem with regards to hard drive size. But I think it might become a problem with regards to download speed.
People with poor data rate won't be able to ever downlaod the chain completely because its growing too fast. This will lead to a decrease in number of full nodes. The HDD isn't the bottleneck with this.
fewer full nodes in remote areas won't be too much of a problem as long as the number keeps increasing in total.