From the looks of it. No. Still can't change weapons.
This skill isn't powerful enough to waste an Ultimate slot. If you plan to change weapons, you would need this skill on both sets, hence wasting an Ultimate slot. Why can't the bear just stay summoned?
It would be like dotting an enemy with the Bow's Poison Injection, then switching to a staff, and the dot goes away. Or using Secluded Grove, then switching sets that has another Ultimate and the spell goes away instantly.
You still wouldn't be able activate the Bear's ability if you switched sets anyways, so he would literally just be soaking some damage, and hitting like a wet noodle. They could even "Nerf" the Bear's damage if you switched weapon sets, so the Bear could deal like 40% less damage if you switch to another set (that didn't have the summon). At least this way, it wouldn't die instantly just because you quickly switch weapon sets, maybe to use another skill.