In the early 80's I worked on systems where 8MB+ was possible with the 8086. So sure a 8MB data structure was possible with a uProcessor a lot sooner than 1989! Now of course the 8086 processor only had 1MB address space so you had to have external memory mapping hardware and other complications like ECC memory because the RAM chips of the day weren't nearly as robust as they are now. We organized the memory as 32 bit wide as it took fewer RAM chips to do it that way considering (data+ecc bits) at the cost of more memory controller logic.

As near as I can tell, the software appetite for memory is insatiable. The semiconductor RAM guys are crunching out more and more memory in smaller and smaller packages, but the hard disk guys are doing the same thing! For the foreseeable future, there will always be a tiered memory system based upon cost, with the cheaper stuff being bigger and slower.

Scalars will never be able to hold "whatever you can throw at them" because whatever the new limit is, somebody will figure out not only how to use it, but figure out a reason to exceed it!