Bad decision. Now we're going to have a huge amount of hacked XF forums in 2020 and beyond. Not to mention the extra work this will bring to some of the forums I run which doesnt have that many visitors (yet). Without no real benefit. Find no thread in on XF forums to complain about this?
I haven't seen one but you could start one I agree it's a decision which doesn't meet my needs but in order to be hacked the software needs a flaw and Xenforo seems to be quite robust in that area. XF 1.5 might remain secure for another five years or it may not. It's the uncertainty that's the issue.
It might remain secure but I would hope they would still issue patches or the likes if not even after their deadline expires. I suppose this is a common problem for developers though, where to draw the line, especially if you're still developing new products.
I hope that if the situation occurs that a significant number of sites are still on xf1 after it no longer gets security/bugfix updates and those webmasters let their license expire, that XF would re-evaluate the situation at that point. But we will see what happens.