+1 to both of mertaals comments
There is a huge amount of potential for the game after GW is done with it. They built a good platform and guidelines for many more additions to be made from the wider world of middle earth. I fully expect O-R to be going for another decade.
There is not much going on in my local area, but there are tournaments aplenty across Australia, so the hobby is definitely on the rise. I'm not anywhere near invested in the Hobbit films as I was with LOTR, neither are most people I know, but they are still going strong.
I plan to get one of everything, and once I have done that, get more and convert it and make community projects. People will be interested in learning to play and paint even though they may have been too young to see the films at release, so don't be surprised if there is a resurgence 5 years after the films.
In terms of playing the game, yes I expect a decline, but still expect there to be at least one tournament in my region each year (this is taking a negative approach and considering Australia is pretty sparsely populated). In truth, I expect the average number of tournaments to drop down to 3 a year, which is enough for me at the moment anyway.
i won't be picking up any other wargames unless there is a large community that sucks me in, but I'll wait and see. I did pick up X-Wing the other day, which I probably shouldn't have given the demographic around me, but you never know.
One last thing which is very important: I suspect we are all comparing the Middle Earth SBG to the 40k scene. 40k has been around for 27 years, basically twice as long as the current version of LOTR. The creativity in the 40k universe captured imaginations and Middle earth can do it just as well, if not better. Once there is more freedom with licencing and so on, there is room for a lot of expansion down the track. 40k was a niche market and still is as no-one really nailed space combat (for me), and lotr has its own niche market in the "fantasy" genre. I love medieval + medieval type fantasy and really despise science fiction except for Star Wars and 40k, so it just goes to show that its not just about the films. 40k is about the story for me, not the minis, hence why I have about 10, and LOTR is about the story too which will never get old.