Wasn't there also a license dispute of some sort which led to the merchandising rights becoming too complicated?
Not when it comes to toys--that one's real simple. Hasbro holds a license from CBS to make a full range of action figures, vehicles, and role play toys like they do their Star Wars, G.I. Joe, and various Marvel Comics (Spider-man, Iron Man, Avengers, etc.) lines.
Hasbro opted to just make Kre-O Trek toys. Their future plans for Trek toys is anyone's guess.