Not really since GPU are the bottleneck usually. The GPU will drag you down in games, but it is not dragging your CPU down in anything. Since thats the definition of a bottleneck the simple answer is, NO!
But the HD4870x2 is getting older now and outdated, it does not have DX11 and to be totally honest, its time for an upgrade of your GPU. Your CPU can handle any card, even tri crossfire.
What would you like to spend on an upgrade?
What PSU do you have?
What resolution do you game at?