It depends.
Is your goal to never work with the state, or do you intend to reconcile with it at some point?
If you never intend to obey laws, then yes. You should stop promoting Tor if Tor becomes illegal.
If you intend to get the law changed back in your favor, then you should continue promoting Tor if Tor becomes illegal.
Up to you.
I'm not advocating compliance here. I'm just challenging this idea that we can beat the state through technical prowess, or that we should do it without being pressed into extraordinary circumstances. It's not just unwise, it's (regarding the "technical prowess") flat incorrect.
There is no such thing as a system that provides privacy only for legal activities. Therefore if you want to fight for the freedom and ability to share information without surveillance, then you must design systems that can, incidentally or otherwise, be used to share drugs (and you must fight attempts to surveil existing systems.)
Should we stop promoting Tor when this inevitably becomes illegal?