Netflix now has over 40 million global subscribers, including over 31 million is the U.S. alone, after reporting strong Q3 2013 results. Domestically, Netflix now has more subscribers than the biggest pay-TV operator (Comcast) and the biggest premium cable network (HBO).

Every research report I've seen continues to verify that to date Netflix is NOT driving cord-cutting (which is relatively small anyway). Still I can't help but ask the question in light of the company's renewed momentum: though it's fully justifiable to consider Netflix as an augment to pay-TV service today, is it fair to continue thinking of it that way forever? In other words, could a very different Netflix - as it might look, say, 3 years from now - become more of a substitute for pay-TV service for certain people?

Consider how significantly Netflix has changed in the past couple of years and how it will continue to change in the next few. Netflix has a strong catalog of popular TV shows and an emerging group of originals that have made it the primary driver of binge-viewing, a whole new model of consumption. Its originals are poised to get stronger going forward. Netflix said it will double its investment in 2014 (though still remain less than 10% of overall content spend), with second seasons of original shows like House of Cards, Orange is the New Black, Derek and Hemlock Grove coming alongside brand-new ones.

As Netflix's originals grow, its value proposition keeps broadening from "watch library content here" to "also watch our great new programs." That's more like HBO's value prop. So ask yourself this question: if HBO were available today without having to first buy-through an expensive bundle of ad-supported cable channels, would it drive any cord-cutting? I think the answer is "yes" - primarily for a segment of viewers that are strictly entertainment-centric and wouldn't mind giving up live sports that are only available on pay-TV (in fact I think the damage that potential cord-cutting would do to Turner cable networks, HBO's sister company in the Time Warner fold, is one very strong reason HBO is so reluctant to go direct to consumer).

Now think of Netflix in this context, 3 years from now, with say 20 originals in its portfolio, some in seasons 3, 4, 5 or 6, with loyal viewers hooked. There are a finite number of hours in a day. As these Netflix loyalists begin to realize how much of their viewing time is now spent on Netflix vs. on pay-TV (which costs them 10x per month as much as Netflix), don't you think some of them (especially price-sensitive and younger ones) will start to realize that they can live on Netflix alone (or maybe combined with some other online video, and/or broadcast TV reception)? Then there's the younger "cord-nevers" that were never pay-TV subscribers in the first place. They grew up on a Netflix diet and are fully satisfied with it and other online sources - how likely are they to become pay-TV subscribers?

Netflix has done a brilliant job of continually hammering home the point that it is not a cord-cutting service, a beneficial positioning since its essential for it to have amicable relations with Hollywood to continue licensing hit programs. But the looming question is how long will this positioning be supported by market reality?

As Netflix gets stronger and stronger, the question of whether Netflix morphs into a bona fide pay-TV substitute for some segment of today's pay-TV subscribers (or would-be subscribers) is going to become more and more pressing.