In an unofficial round about way, yes. Ubuntu is based on debian. So it's near 100% compatibility. So using debian sid / fienix packages it's pretty easy to update most of the installed Ubuntu 16 software. Just be patient, and selective, and you should be ok. My PowerBook g4 is now 70% updated from 16.04.
Due note however I did have to reinstall a few times because I pushed the issue and tried forcing some stubborn packages, or didn't pay attention to what might be removed by installing other software. For instance updating synaptic removed lubuntu-desktop.
So I wouldn't advise it, unless you have no sensitive info you want to keep and you aren't afraid to hack around a bit.
Cheers