Unless the exact original part is needed, I jump at the chance to actually upgrade any Shimano 8s road bike with one of SRAM's inexpensive cassettes. These cassettes have much nicer finish and are quite a bit lighter than Dura-Ace 8s cassettes due to more extensive perforation of the cog blanks. I for one am really glad to be able to buy these, as well as the equally-nice 12-32t 7-speed cassette that SRAM has been offering.

So I see no problem with sourcing good cassettes in the future, but hoods for old STI levers could be an issue at some point, as they so often have.
I have sourced good hoods from my big pile of broken STI shifters, which kind of makes my day.

I have stocked up on Sunrace 13-25t 7s freewheels just in case they were to change their look (like Shimano did) or stop making them.