There are a couple of other options that poped into my lil' old head.
1. After Data turned off Lore. Was it ever mentioned whatever happed to Lore's parts? I doubt Data left him behind (fear of possibility reassembly). Lore was most likely put in a storage container somewhere. The Daystrom Inst. could eventually come into possession of Lore, and try a drastic experiment - Wipe Lore's processor clean, and try to download Data from B4. It'd be an interesting concept to explore - Data exploring remorse that Lore was totally sacrificed to being Data back, along with ghost flashes of Lore within Data's matrix. (Just a thought)...
But deactivating Lore is the equivalent to putting a biological being in long term stasis. There's still some slim prospect someone in the future might find a way to safely rehabilitate him. We're not even sure member planets allow capital punishment. Unless you found some way to back Lore up in some other device, overwriting Lore's personality with some combination of his "brothers" and "niece" would amout to execution. Even backing his personality up and replacing his personality could be considered slavery.
I wasn't suggesting that the procedure would be fully sanctioned/legal by Starfleet. (added drama/conflict).