OK, appears you have two separate areas. X610456.JPG being the top sinus area. The third tooth from the back "IS" (sorry) abscessed. (By the way, did you have sinus surgery in the past on this top area?)
Generally when abscessed, a tooth does hurt, true. But not always, and/or not always full time either. But, I understand your concern, as in, why do a root canal? I think you are going to relatively soon, be best off getting a root canal on this bicuspid on the top. Some good news: It's generally only got 1 canal, so it's quicker to do, and costs you less than other molars with multiple roots.
With regard to X610456_9.JPG - It appears to be a lower bicuspid. It "may" be abscessed, and then it may not. Let me explain. Other x-rays are needed for the lower. The lower is more difficult to say the dark halo under the root is for certain an abscess, or, is it the "mental foramen", something which mimics an abscess, but only on the lower bicuspid area.
Summarizing: The top bicuspid does have an abscess. Does have need, even if you don't yet feel anything, of a root canal (1 canal generally only).
The lower bicuspid, more x-rays are needed to be certain as to whether it does or does not have an abscess. Did your Dentist suggest you have one or two abscesses?