You're not going to be forced to steal them, there will be lots of lootable containers in the world.
The drop rate (more to point spawn rate) will not change in 1.6. So if you farm them for yourself and your alts, it won't change a thing for you. It's only those who farm Motifs to sell that will possibly be impacted. Anything stolen cannot be sold to another Player, only vendored to a Fence or consumed by your account. @Ahdora is also correct, there will be TONS of containers that are not "owned" by any NPC and can be freely looted at will and the contents sold to others.
That said, will some Players take advantage of this change to jack up prices hoping to make a quick buck? YOU BET THEY WILL!!