In the past, technology like the horse drawn carriage was fairly simple in that one person could understand it all. Now we have massive things like aircraft carriers that have nuclear powered engines, Linux OS, and probably millions of lines of code and bells/whistles. If we eventually get to the point where we aren't junking these systems every few decades, who will maintain all the technology and code?

Will we reach a point where nobody understands and can fix much of our infrastructure?

It doesn't seem problematic now, but if Moore's law's effect completely stops and we can't make new progress like the rapid changes in computing we've seen since the 50's, I think we'll enter an ice age where we're re-using computers and machines for much longer periods of time. I don't think any of our software is designed for that though.