Yeah, I'll be pushing 80, Bobvfr has a great point there.
It's 2038, because of wrap-around (simple version), 32 bit won't be enough to go from 1901 beyond that date. You can look up the Wiki or similar if you're bored/interested ;-]
Edit Wiki pointer:
https://en.wikipedia.org/wiki/Year_2038_problem
There are undoubtedly embedded things that will be an issue then, but not our phones.
And like EspHack mentions, 4GB is a much bigger concern than any other issue, really.
The seriously scary thing has probably more to do with things like medical devices and military stuff, that could still be in use then, but fails to function correctly at that date/time.
RS was rumored to be 64, on capable phones, but something happened. Maybe it's the RAM issues/pricing mentioned above, maybe it's the "thunk" that's in the ARM chips and processing/power problems, I'm not sure, I haven't read into it much...
This was a problem in x64/amd64 for awhile, until the processor manufacturers added calls for PhysToVirt and VirtToPhys, and made them part of the core, so that they were highly efficient, before that, there was was concern about thunks on desktop machines, and the big processing cost.
I do remember having this big debate, and being marveled by the couple of 4GB machines, the debate being if we would ever actually need 4GB, for "real world computing", not just some big server ;-]