I bought EQ7 about a year ago (I'd had old versions, but none were upgradable). At the time I asked the company if they were planning an upgrade. They said not in the foreseeable future because they couldn't think of anything new they needed to do. Just one year later, here's the upgrade.
So my answer about whether I'll upgrade: Not in the foreseeable future, because according to them, there's nothing new they needed to do :-). If EQ8 is anything like EQ7, it's on a many year release cycle, so I can wait until the upgrade price gets better through resellers.