Not launching for awhile for reasons of battery life might be a good thing. Apple often gets/buys access to the latest newest tech in actual production, so that means the watch might get better batteries than anyone else is currently using in volume.
On the flip side, and let's be honest here.
History has told us that Apple, for mobile products does not place battery life very high up the list.
They seem to have decided that 1 day's use is what THEY THINK you should have.
Irrespective of what YOU want, that's Apple playing Mummy and Daddy, as always and deciding what's best for you.
If you look back over years on these very forums about iPad, and iPhone battery life.
there are postings upon posting from many many people almost pleading that Apple stops making the next product 1mm or 2mm thinner, but rather keep the same thickness and improve the battery life over the current model.
But they won't listen, and will thin the next model down, at the expense of the battery. I think the iPad Air 2, has a worse battery life than the iPad Air does it not? Simply as they put, and I have to use the well used term again:
Form over function.
That, I'm afraid IS the problem with Apple, they give you no choice.
You either buy the 1 model they offer, or you move away from Apple so you are stuck.
Like now, you want the latest phone last year, but you wanted a BIG screen, sorry, 4" was the size, and 4" was correct.
This year, someone else loved 4" but wanted the new phone, sorry, we are not making that in 4"
Give people the choice, and people will buy what THEY want from Apple's range. But it makes Apple more money to make the 1 model.
Without ANY question whatsoever, if Apple DID add, say 2mm to the thickness of this years iPad or iPhone, and sold them both alongside the current models, as "Long Life" versions.
You can bet, a TON of people would buy the long life versions, with say twice the battery life.
I think Apple seem to consider, hey, you charge your iPhone every day, so you are happy with that, so you will be happy to charge your watch every day also.
Whilst I'd love to be wrong. I can't see Apple struggling to make the watch last for days and days on a charge, they would rather make it thinner, faster, add more things to it, than add days of battery life.
I hope I'm wrong.