No. Infusing only works by using a [b][i][u]STRONGER[/u][/i][/b] weapon. So, higher base stats. And it only works on ttk weapons. It looks like the old exotics will be 160 dmg. You can't use them on the 180 legendaries from ttk. The weapon can be at any stage in it's upgrade path, just like ascension. I didn't see any damage upgrade nodes in the reveal, so it looks like brand new weapons will work as infusion material.