Is this confirmed somewhere or a fan theory? I looked into it because I wanted to see the juicy details of the beef, but I can't see anything to support the "WotC screwed Lucasfilm" interpretation. I can't see any reporting of pending lawsuits or anything and it doesn't seem to fit the facts.
The Star Wars Miniatures Game existed for six years. It seems very unlikely that Lucasfilm was just "surprised" by them doing this, and then just didn't take any action at all from 2004, until 2010, then suddenly lawsuits! That would be pretty weird to put it mildly. Lucasfilm are litigious and if WotC had violated their contract, they'd have been all over them.
What I can see is a lot of complaining from people that the quality of the minis was going down drastically, and that the "reboot" of the line (not sure exactly when this was? 2007 or 2008?) was surprisingly unsuccessful, despite apparently improving things somewhat, and that by 2008 the products were no longer selling well (piecing together various threads on various forums, particularly Boardgamegeek, here).
Then in 2010, WotC announce that they're dropping the line and the RPG. They blame "the economic downturn", which is meaningless because everyone blamed it for everything, but I can't find anything from the time saying "Actually there were lawsuits!" or "Lucasfilm actually didn't want them to renew it!" or anything of the sort. The official Lucasfilm line was the same (on StarWars.com). Given that the minis had reported poor sales, and that interest in Star Wars was not particularly high in 2010 (two years before Disney bought Lucasfilm), I feel like, unless you have at least some more specific scuttlebutt, this is probably a case of fans making up a cool story, rather than a thing that happened.