The only problem that I would have is that if there were to be a Season 5, would be the cost. I remember reading something a few years ago that said that each season cost somewhere in the region of US$32 million to produce - now you would have to figure, that amount today would be in the region of $50-55 million...that's a hell of a lot of capital to raise! Where would that money come from? ( and yes, I'm spitballing here, but for the sake of argument, let us take those figures as written for a moment)...I don't think Netflix would see that as a viable outlay. Even with external investment, I seriously doubt that money could be raised.
I actually think the cost of FX is getting lower, not higher. Also, look at the quality of the fan made Trek shows. The FX is nearly as good as if not better than some of the FX seen in TNG and these guys are not spending anywhere near the numbers you mentioned. I'm also sure Doug Drexler, Mike Okuda, and many others would volunteer to build all new sets for a new season of Enterprise.