Not to disagree with anyone but as mentioned before (& unlike warhammer 40k, sigmar, etc) GW has to basically buy a liscence from the tolkien estate (or whoever owns the rights) to produce their middle-earth products. This in turn will place more emphasis on making sure the models are as close as possible to the movie counterparts as well as balancing their own costs against those of their customers ; which in turn can potentially mean a slower production rate. By all accounts 40k is their biggest moneyspinner so that is why the middle-earth range will always (appear to) come lower down their list of priorities ; it's not that they aren't interested in working on the range, just a business plan, pure & simple
That being said, I do think that they could be a bit more forthcoming about new releases or trickle little snippets of news / sneak peeks more regulary to keep middle-earth up with their other miniature releases ; also it does place more emphasis upon us to keep the hobby alive by supporting them and one factor that is a big influence (& often overlooked) is that unlike their own 40k line, they are producing models for a series of books & films that fans have cared
passionately about for
years.
They just do not have that much free rein to go mad and produce loads of models that may not meet the majority of peoples expectations & therefore be met with a backlash or not sell well at all (swan knights of dol amroth for example...). It is clear that they will be supporting middle-earth for quite a few years yet & I have no doubt that we will all continue to see more fantastic models for middle-earth being released. If that is at a slower rate than we would like, then it may be something we have to live with.
I take heart & enjoy the fact that with our support, they have managed to keep the line alive / in production for 16-17 years already, which is not something that they even managed with some other good properties of their own, such as bloodbowl. Middle-earth is here to stay for the forseeable