Hopefully it doesn't. I use Gnome3 on a tiny 9 inch netbook and I hate running simple little tools that use memory like the integrity of the universe depends on them. Limiting the choices developers have will make sure that all extentions are just JS and everything will stay lean, mean and without bloat. I don't care if I have to wait for extentions a few years longer or if I will never get them. If they are really important they will be done in JS othewise I don't want to be bothered with them. If there are crappy Python, Perl, Ruby, Java (insert bloated runtime crap here) extensions there will be less incentive to develop them in JS, which is already there and fairly lean and fast. Millions are invested every year to make JS fast and efficient (compared to the 5 bucks that were spend the last decade to make CPython or Perl fast..(not counting Unladen Swallow etc.))
The Gnome developers intent Gnome3 to be used on resource limited devices and limiting developers to use the tools that are best for user experience is the best way to success(see iPhone).
Gnome3 focus hopefully is more on user experience than on developer experience. In the long run users are much more important. Even developers will cope with crap if the user experience is great.
It's FOSS so you could do whatever, but I hope the Gnome devs have the foresight to not encourage slow bloat.