I'm hanging onto my earthstone, even after the update. I know I would get a boat load of cash if I sold everything before the update, and after it will definitely go down in price. I'm keeping mine because it makes leveling alts easier. I've been working on my alts lately, and it helps a lot having this gear availlable to me. You can also focus on leveling without having to stop and worry about picking up frags/meteor upgrades/crests/orbs. So while radiant earthstone might not be all that great on levels 150 to 180, it will still be valuable for levels 100 to 150.
If you are going to sell it though, do it before the update because the price will go down. If you're looking to buy, do it after the update because... the price will go down
rad earthstone bp is not really op in all aspect cuz of low armor and no elem resist, it is op on dmging tho cuz of its attack and heat dmg combination. i would say that it will be the most priced bp for a long time so if i were u, do not sell it unless u have extra

A lot of people say rad ES is not overpowered because of the low armor, but don't take into account the evasion stats on it. Who cares about armor when you're dodging almost every attack?