Linux currently has time_t as 32 bits on Linux 32 bit. This will run out in less than 25 years (mortgage times) and Linux is being used embedded in devices with long > 10 year lifetimes (cars). Is there an upgrade plan for this platform?
There is no "set" time or time frame for which all Linux kernels will be using 64-bit time_t. In fact right now the general consensus is that it will not be changed anytime soon. No one is really that worried about it yet; just like Y2K it will cause problems in code that already relies on time_t.
There are a few Operating Systems that are using the workaround which is to use a wrapper that makes time_t both a 32-bit and a 64-bit integer.
While others have just forcibly upgraded time_t to use 64-bit integers.
For more information please refer to this link: https://en.wikipedia.org/wiki/Year_2038_problem