Come April 2016, Intel 32-bit users might be on their last, overdue leg for upgrading their distribution. Quigley is considering a proposal to kill off the 32-bit install (ISO) images after that point while support for 32-bit applications on 64-bit Ubuntu would still be supported. The proposal would only involve Intel/AMD x86 with 32-bit ARM being unaffected given that 32-bit ARM is still very common to devices.
For help building this proposal, Bryan Quigley is requesting people take a short survey that can be found via this web page as he tries to get a better idea for Ubuntu user habits and what kind of hardware they're running.
If your hardware is x86_64, you should definitely be running 64-bit Ubuntu! The performance is much better and there's really no reason to be sticking to 32-bit Ubuntu given that all of the incompatibility issues of the past have been pretty much resolved. With ending the 32-bit Ubuntu installer releases after 16.04 LTS, that would still give devout 32-bit users until 2021 (five years of LTS updates) to let their hardware gracefully kick the bucket.