I pretty much disagree with everything in the OP so I'm going to say ... no new edition in foreseeable future. I could see a book with a significant set of options that would change some things around and give people suggestions on how to tailor the game to their group.
It's pretty obvious they're working on a new book or two with new classes, feats and an expanded ruleset. But that's a long way from a new version.
The following is IMHO of course. Mearls uttered the words 6E and of course this leads to speculation that they are working oin 6E or that 5E is not doing very well.
Now the problem is that online people tend to lean towards extremes. Generally there are posters who think that 5E is the best edition ever (personally its in my top 3, best ever doubtful), and that 5E is perfect and will last for 10-20 years or will be the last one.
Others have been predicting 5E will die a miserable whimpering death. This group is mostly 4E fans who were miffed 5E was not 4.5.
SOme people claim 5E is the best selling D&D ever (its not), but it has probably outsold the other editions since 2003.
Another example would be some posters who think 5E is perfect mechanically where there are holes starting to be found and they have been contradicted by Mearls when they argue things like RAI vs RAW. Off the top of my head there are a few mechanical issues 5E has.
1. The -5/+10 feats
Ok. These can get pretty ridiculous, but nothing a DM can't handle. They could also be deprecated?
2. Bonus actions
I don't know where these are a problem. They seem to do a really good job managing the action economy.
3. Saves at higher levels
What's wrong with them?
4. The way ACs scale at high levels (Monsters start getting +10-+16 to hit, ACs, are still around 20)
You expect ancient dragons to pull their punches?
5. Some classes/archtypes
They can't be supplemented/deprecated?
6. Advantage
What's wrong with it?
7. Concentration mechanics
What's wrong with it?
8. Casting multiple spells per round
What's wrong with it?
Some of these effects are underpowered, overpowered, maybe broken, or just complicated.
WotC has indicated they are gonna be moving away from the AP type adventures and that 6E will land when the players want it (AKA when 5E sales decline).
So how long will 5E last.
The bare minimum if they started designing 6E tomorrow would be 6 years. I do not expect this.
In it lasts a decade or more that is great but only 3/7 D&Ds have done this (1E, 2E and BECMI). I would put 10 years at the upper limit. 3E in all its various forms has lasted 17 years, this is coming close to BECMI's 19 year record (if you count Paizo's Pathfinder as 3.x).
No WoTC D&D has lasted more than 5 years in print, 8 if you count 3.0+3.5.
So if I was a betting man (I'm not BTW) I would expect 5E to last in the 8-10 year range. 6E will come eventually when that will be IDK.
Personally I hope that at the 10 year mark they release a new revision of 5 with new rule books that consolidate a bunch of what comes out between 2014 and then.
I think to a certain degree it may depend on how well the movie does.
HASBRO has tried several times now to leverage their intellectual property into mass market movies with mixed success. By most accounts, Marvel now makes more money from movies than from comics. If D&D movies are anywhere near as successful as the MCU then the books that we know and love just become a subsidiary of the D&D franchise. We might see action figures, but the majority of the profit wouldn't be coming from the sale of books anymore. The RP game could just be an advertising arm of the movie franchise.
There's no guarantee there will be more than one movie seeing how some fantasy based movies have fared, but I'm cautiously optimistic. It will be interesting to see how, or if, they impact the book side of the equation.

(Dungeons & Dragons)
Rulebook featuring "high magic" options, including a host of new spells.