A few days before the release of the Forsaken expansion for Destiny 2, Bungie warns players not to infuse new Year 2 items into Year 1 gear. If you are not careful, some gear pieces could become unusable until Forsaken.

With the Forsaken release, the character and power level in Destiny 2 will be raised. And already now Year 2 gear drops with power values beyond Year 1. Numerous Guardians are now trying to infuse into the best possible starting position for the launch of the fall expansion. However, Bungie urges Guardians to exercise caution.
What you should consider when infusing your gear until Forsaken
Currently, there is a risk that players could make their gear unusable when infusing – at least until Forsaken.
Pay attention to the level requirement: As the power level of the gear increases, so does the minimum character level required to equip that item. You can tell because the corresponding items are grayed out and display “Level X required” in a red tooltip.

Caution when infusing: If such a Year 2 item is infused into your Year 1 gear to raise its power level, the affected item, whether it is armor or a weapon, will be locked and can no longer be used by you – at least until you reach the necessary character level after the launch of Forsaken. Only then can this gear be reused.
Because the level requirement is transferred from the infusion material to the target item.
If you infuse a 410 weapon from the second year into your Better Devils, you will need to reach character level 32 before you can use the hand cannon again. So be careful when infusing what level the items have that you want to use for infusion. Otherwise, you risk locking your current gear.