the T3i, 60D, and 7D are all virtually identical in video performance. You really don't see an increase in lowlight performance until you jump to a full frame camera or a cinema camera. Within the crop sensor range, its really not worth spending the extra money on the 7D as it has virtually the same video capabilities as the 60D and t3i.
that being said, if you really really really want the lowlight capabilities, the 6D is the new less expensive full frame option.. though still $2000 for the body alone. (don't quote me on this but I believe it has the same sensor as the 5DmkIII)
But yeah, if you're not going to be paying a whole lot for the 60D after you sell the t3i, then its a great deal. you'd get the weather sealing for next to no money. I say jump on that opportunity