It really comes down to execution and timeframe. If they abandoned the current chassis design tomorrow it would be a problem. It's hard to predict exactly where things will be in 10+ years and to expect that the current chassis will be the best design for a computer in 2035 is very hopeful. At some point the current chassis might be a technology limiter preventing adoption of some new standard that most people will want.

I'd hope even if they launch a new chassis they continued to make new boards for the old chassis for a period of time. I'd expect in the end they will continue to make new boards for the current chassis until there isn't enough sales to justify it. Maybe in later years of chassis support they might skip some generations of CPUs and only launch a new board every few years or something. I'm hopeful of many years of support for the current chassis and a fair amount of overlap if they adopt a new chassis.