Just to be clear, I'm not proposing that Ubuntu MATE absolutely want to continue providing 32bit iso images.
My daughter has a Dell Mini 9 Atom netbook, it is 32bit only. I think netbooks are in the category of computers sold fairly recently that are still very usable. However, the main concern for me is how often do organisations such as FixIT - Leeds Coop and Reglue receive 32bit PC hardware donations? And how this decision affects them and the families and organisations they support who simply don't have the money to spend on a computer. I also volunteer for an organisation that refurbishes donated computers and ships them to schools in Malawi.
I have some statistics for the Ubuntu MATE downloads and the i386 downloads are a tiny percentage when compared to amd64 and armhf (Raspberry Pi). That said, the number of blind and visually impaired individuals using Ubuntu MATE is also extremely small but I continue to invest the effort to ensure Ubuntu MATE is highly accessible. Likewise I would be prepared to continue supporting i386 while there is a socially valuable reason to do so.
With that said, if the Ubuntu Security team determine that maintaining the security profile of i386 is not possible, with particular regard to browsers, then that would undoubtedly influence my thinking. I'm simply not prepared to release a desktop operating system that has inadequate security coverage. We've got some polls running in the various Ubuntu MATE communities to survey what hardware people have access to and I've reached out to some of the charities that make use of Ubuntu MATE to better understand how, or if, this decision might affect them and the work they do.