No I'm sorry. Removing the sidebar display does just that and nothing more. It does not create an expansion of the posting area. If you are using a wide screen display please be aware that many readers will not be viewing your blog on big screens. Many will be viewing form laptops and mobiles, etc. The avaerge screen resolution size is 1024 x 768.
People on widescreen (if you are talking about big, wide monitors) are actually quite rare.
1024x768 -- 40.28%
1280x1024 -- 16.97%
1280x800 -- 16.89%
1440x900 -- 7.71%
1680x1050 -- 4.28%
800x600 -- 4.01%
That means over 78% of people are on resolutions of 1280 px wide or less.