As several people have pointed out, the franchise is saturated... there is a lot of material out there for people to watch.
The franchise isn't at all saturated. People pay attention to what gets shoved in their face, and not much else. The existence of 600
Star Trek episodes (or whatever) really doesn't count for all that much because it's not shiny and new and being waggled in front of everyone's face.
Imagine how many episodes of
Gunsmoke there are in existence! That frakkin show ran for 20 years. Is
Gunsmoke "saturated"? I'll bet before I just mentioned it you hadn't thought of it in a long time, if ever. That goes to show how hard it is to keep anything in the public eye.
Plus there's another factor... fan fiction productions are going to keep gaining momentum.
Fan produced material doesn't mean anything to the corporate honchos who will be looking for ways to capitalize on the success of
Star Trek XI. If you want to predict their behavior, just ask yourself: how can I make the most money off this thing? One obvious answer, if there's the momentum of success caused by a hit movie, you jump right on that momentum and don't let it be lost. Momentum dissapates quickly as people are distracted by the next shiny thing being waggled in their face.
Down the road, if we end up with a couple of decent quality fan fiction productions, it'll be one less reason to embark on another big studio Star Trek series--it's already being done.
The people who own the license to make
Trek aren't going to make money off these productions, so why should they factor into their calculations? If they pay attention at all, it would be to shut the productions down, assuming they ever reach the point of being competition. Maybe someday fan productions will be good enough to be worth people paying for. That's the point at which the lawyers swoop in and kill the whole thing off.
Seldom does a series started from a movie end up doing well.
Since the movie started from a series, your example is irrelevant. The actual situation is TV to movie back to TV (more than once, too).
Star Trek has a unique ping-pong history going between TV and movies, which has made people quite a lot of money over the years. The corporate honchos are not likely to ignore that.
Because there are so many viewing channels, and competition from GAMING and INTERNET, the days of massive audiences watching a genre show (nuBSG proved this) are long over.
That poses a challenge to
Star Trek on TV but it poses a challenge to everything on TV that isn't a reality show or a cop/laywer/doctor show. That doesn't just mean TV producers throw up their hands and admit defeat. It's their job to overcome obstacles like that.
And
BSG proved that even a pretty off-putting genre show (far more prickly and difficult to get into than
Star Trek is ever likely to be) can survive for four years on TV, with audiences that play in the 1M-3M range - a truly puny number. But who cares what the number is, if the balance sheet is in the black, taking into account all the factors - production costs, ad revenues, overseas revenues, merchandising revenues, DVD sales, etc. There are ways to make the total mix work out, and a lot of it is based on figures we'll never see.
While ENT was still on, I remember reading here that it regularly lost out to BSG. Is it more successful in re-runs? 
all people care about now is reality tv or crime drama. maybe things will change? after all there is supposed to be another stargate series coming out. but i would love to see another ship with a brand new crew. partly the problem, is that the production of trek is so, erm... simple? the special effects werent great, but they did the job perfectly. and the sets were clean and simple.if a new trek series came out i doubt it would be like it was. i think it will all be bare metal and pipes. i am not sure what will happen in the future of trek. i just hope it never dies.
