I have both architectures, only very recently (1 moth ago) having acquired my first 64-bit computer.
However, I live in Angola. The vast majority of the computer market is 32-bit computing and most of the people I know operate 32-bit computers. 64-bit computing is rarer, even more so because its exactly in these 3rd-world markets that the large manufacturers came to dump all their 32-bit stock. It's for this reason that you can still buy in here new, never used, 32-bit computers even today in 2016. 64-bit shows up, but its just not that attractive to home or SMBs because it comes at a higher price.
This is a tough thing for me to speak about because Ubuntu-MATE is not Canonical, so I can understand perfectly well if eventually 32-bit is abandoned because the upstream repos have abandoned it. Ubuntu-MATE would need a strong influx of package maintainers to keep up with the work and start their own repos.
It's for this reason that whatever I replied to another post (linked below) discussing this matter has nothing, absolutely nothing, to do with you guys. I always tend to frame my opinions on the people that need to make the decision. Not just on how that decision may impact me. And in this case, that is you, Ubuntu MATE team and your reality in terms of personal and infrastructure. Which I understand if you will be very likely forced to follow Canonical decision.