Absolutely not. The 1gb ram in 99% of the games at any amount of 'playable' AA levels is not a bottleneck.
You can look up gtx 460~768 SLI that performs well in most games at 1080P. 99% of them.
Except in Metro 2033 at some AA levels and Crysis at some levels, settings @1080p.
edit: Now looking at your post, I'm a little confused how your using the term bottleneck, for what your describing. I thought you were asking about frame buffer limitations.