GW already have a load of good miniatures (and a few bad exceptions) based on the movies, and another load of mainly even better miniatures based on the books and their own interpretation.
With the coming Hobbit releases GW should be careful to establish Lotr as a recognized wargame on par with Warhammer and 40k. Major issues here might be the rules and force organizations, for these must be appealing. The rules should keep Lotr a skirmisher game (with Wotr for larger battles), but perhaps a few tweaks are needed in order to bring the playability and gaming experience to the same level as Warhammer and 40k? The introduction of banners, Goblin Drums, shamans and other minor heroes was a step in the right direction because it added texture to the game and made it less dependant on the named heroes.
After all, playing with Aragorn and Legolas might be all right, but a lot of collectors will theme their army around a general of their own, with lieutnenants of their own. Adding minor heroes not seen in the movies, but either invented (such as Murin and Drár, or Groblog) or from the book (such as Cirion) was also right to do, because it added to the rich texture of the wargame.
As for the force organizations, these will have to be more or less set in stone after the movie releases, or preferably along with them. Should GW release army books or codexes dealing with parts of the good or evil side, or should they release everything in one rulebook, or is it better to have one dedicated rulebook (along with background material, maps, collecting, painting and even conversion pages akin to the WHFB rulebook, thank you) and two large army books, one for Good and one for Evil?
How shall the game be expanded further? Obviously there are a lot of interest in a Last Alliance release wave, and if it had been possible a departure into Silmarillion realms - mainly with loads of Elven miniatures added to the ones already available - could be succesful, especially if the main tales of the Quenta Silmarillion is treated with backgorund, campaign, scenario, rules and hobby material. For a Wargame this would not only be Beren & Luthien, Túrin Turambar, and Gondolin's Fall, but also the Darkening of Valinor & Fëanor's kinslaying and the various battles that were fought in Beleriand. But are Supplements a feasible way to go? Perhaps, but then the vast majority of profiles and stat lines should be collected in established force books (whether the rule book or various army books).
Further on, for Lotr to become established, it must be given support through White Dwarf, GW stores and tournaments and the GW website. One thing that to me always seemed lacking with Lotr, even after a lot of improvements had been made, was how it didn't appear to have the same hobby and wargaming depth as WHFB and 40k. The lack of multi-part plastics is an issue, but not a lethal one in itself, just as the different scale to Warhammer prevents people from buying Lotr elf archers for WHFB High Elves is an issue, but not a devastating one. Perhaps some metal bitz packs should be released for Lotr through the web store, along with regular conversion articles of every kind, especially if coupled with such things as warband and campaign articles. Non-GW staff hobbyists should be given some space, preferably through Tale of Four Gamers. Professional painting articles must be encouraged. Battle reports also need to be improved.
I personally think the skirmish nature of the Lotr game to be well suited for campaigns, especially if based on movie and book stories, so why not sneak in some Mighty Empires tiles, set up a WD campaign and follow this for a month or three. Terrain articles nowadays centres on GW's plastic kits, but for Lotr some old fashioned DIY-articles would be in order, just as the Helms Deep one was. Ship building could be combined with rules and battle reports about naval combat, and tunnel fights could be explored further. Point out the advantages of Lotr as a Fantasy skirmish system and try to sell its niche between 40k and WHFB.
In short, GW needs to give Lotr more depth to establish it, which as Dr Grant points out is somewhat anathema to WD's current catalogue status. GW should want to reap profit from Lotr for a long time to come, just as they do with WHFB and 40k. Then we have the issue of GW's pricing policy, but that one is not Lotr-specific...