"First of all, you did not cite market share numbers to show lack of an effective monopoly..."
"Netscape was a monopoly in effect (it's very rare for a real-world monopoly to have 100% of the market)..."
I don't think you know what the word monopoly means. Market-share is entirely irrelevant. What constitutes the definition (the reason the term even exists: what is meant to describe) is not how "big" a company is, but the _exclusivity_ (as in: is anyone else allowed to ENTER that sector of the market). And using the words "effective monopoly" or "in practice/real world" doesn't work as a permission to misuse the term, either. In fact, it does the opposite. Actual real-world "effective" monopolies would be: An entity holding a patent for some invention, the State having exclusive control of force, etc, etc.
Some company being "the only company who is currently doing X" is not a monopoly, as long as anyone else can enter the market.
Dart is probably going to suck, though (and Java-stained ideas polluting its design will probably be the cause). Also, unless Chrome wants to commit suicide, it's gonna keep supporting JS in the current and future versions, so you JS people should put a halt to this soap opera. Pause thy bitchfest.
Whatever you call it, if Google had that now or very soon, it could indeed ship new stuff and "make it stick". Since it doesn't have that power, I repeat that Dart is fragmenting.
No one is obligated to work on extending existing standards only, not try injecting new ones. Doing both without market power to make the new ones stick is going to make a mess in my view. I keep saying this, do you disagree?
I'm the last person who wants to save JS from extinction. If it were cheap enough to kill, I'd do the deed myself. It's not cheap to kill -- quite the reverse -- and the leaked memo's assertions about it being unfixable are exaggerations at best, and betray a significant conflict within Google.
(BTW I agree there's a smell of "Java-stained ideas polluting [Dart's] design.")
If TC39 had a crack at standardizing Dart or putting ideas from it into ES6, everyone would be better off -- even if Google then launched Dart anyway.
Instead, while we in TC39 were working in the open on ES6 (which is past new-proposal freeze), we knew nothing. That is not just missed opportunity, I call it poor stewardship on Google's part.