4e might currently be popular in your area/circle, but according to sales globally, Pathfinder is currently selling better. There is of course the period were 4E was selling better then Pathfinder and the period were there was 4E and no Pathfinder RPG for sale, so total sales over it's life 4E still has an advantage. But that's not how publishers see things, less sales, or even worse, less sales then the main competition (that was working for you just a few odd years ago) means your in trouble (and they are right). That's often when companies start to panic and do odd things (like last years new core range), or even worse, desperate things that might blow up in their face.
in the 3(.5)E era D&D was the big fish (post nWoD), had close to 90% of the RPG market in it's grip and most of the rest of that market was directly linked to D&D through it's ruleset. 4E broke the fanbase worse then it ever did before, not to mention that they alienated a lot of 3rd party publishers with their move away from the OGL. Even those that initially stayed with 4E eventually didn't. A lot of publishers either threw in the towel, did their own new rules set, or stayed with the old OGL. That means far less threads that lead back to 4E to fill in holes that 4E doesn't fill itself. So I doubt that 4E even covers 40% the RPG market, the RPG market has also become smaller thanks to computers (MMORPGs), so WotC/Hasbro is raking in far less then it did in the 3(.5)E days and that worries corporate, which in turn worries the investors. And Hasbro doesn't have the best track record for properties, the End of G.I.Joe in 92-94 was horrible with gaudy looking toys (use of neon colors, eco-squad, star-squad, sky-patrol) and ripe with horrible looking reissues (neon green doesn't make a Cobra vehicle look cooler!). It was almost a decade before we saw a proper relaunch...
What I'm trying to say is that WotC/Hasbro has a bad track record with 4E, there are a lot of folks really happy with what 4E does (and doesn't do), why risk this group when a 5E might further fracture this group. Sure a 5E might redirect some Pathfinder and other RPG fans to 5E, but imho the new players attracted would never weigh up against the players lost. Just like 4E didn't attract oodles of brand new RPG fans, 5E wouldn't suddenly change that situation.
Another issue with 4E is that it's mostly crunch books and relatively little fluff. That makes the books people have very useless when a new (and completely different) D&D version shows up. I used my 2E Forgotten Realms books for my 3E FR campaign extensively, the same could be done with a lot of the 3E books, but 4E just doesn't have the fluff imho to be useful. So a lot of 4E folks would feel a lot more 'betrayed' by a new edition then 3E ever did, because 90% of the books they have is now completely useless (compared to maybe 50% from 3E to 4E).
I also see an issue with product accessories, thing from miniatures, to battlemaps, to cards, to coins, dice, etc. WotC/Hasbro has been killing off those accessories for D&D 4E, Paizo has been making those accessories for Pathfinder. While not everyone wants those things, a lot of DM/GMs do, and generally those opinions count more then the players. I suspect that we have a 10-20% customer group that dictates what is played in groups (within reason) and WotC/Hasbro just isn't providing the toys they want/need. A lot of us are already drowning in minis, cards, dice etc. But what of the new generation of DM/GMs?