Chrome already supports extensions, Adsweep works on Chrome as an alternative of ABplus. Noscript is used by a very small niche users, I seriously doubt noscript users are holding Chrome back on mass adoption.
I think switching browser is always a difficult choice for non tech savvy users. Personally it was a hard choice for me 4-5 years ago to leave IE for FF, but it was easier for me to make the switch to Chrome after I used it and liked it. I think my view towards a browser changed over the last 4-5 years and I see a "browser" as a tool as opposed to a gateway to the internet. I think most of the early adopters of Chrome are fairly tech savvy users and for chrome to be really mainstream they need to push chrome bundled with new computers (I think they already do that).
Chrome is awesome and it can only get better. I hope Google Chrome OS will be just as good.