This link is also very useful to better understand the new system :
Dadi’s guide to new LI system
From what I gathered from this post and the lotro forums, my conclusion is it’s urgent to wait !
All the changes in Bullroarer are still work in progress, far from being definitive. So it’s best to wait till they are before taking any decision.
It’s not hard to wait if you already have your 1st age lvl 100 LI maxed out. If you’re looking into building one, my advice would be to have a good look at the legacies that are going to change for your class, so you don’t end up with something you don’t want. Even so, there is no guarantee, as this is the part where it’s likely there’s gonna be the most changes.
Finally, I won’t rush in to imbue my weapon when the update goes live either, because it seems cheaper to upgrade before imbuement rather than post imbuement. And you’re still not guaranteed to be able to get your weapon at the level it was before.