Hope 'wearable' gets as far away from this as possible...
but serious now, I think Google Glass will get popullar, just not now. A watch is bigger, and get's more stuff in it.
Samsung and Sony aren't the first companies to risk themselves into smartwatches, so research is much more extensive then that of smart-'glasses'.
Since a watch is also bigger than the space you would have in some glasses, bigger components can fill the board.
The technology needed to put into them needs to be much smaller, therefore needing more time than a watch.
As a second part, a watch is something you can wear every day, As with glasses it would be a much bigger change to walk around every day with expensive glasses on.
I wouldn't want to wear them all day either.
So that's my opinion; The smartwatch will get popular at first, but when Google Glass is ready, it will take over...