Eventually it will darken. But you can fix it after partially bleaching so that it won't darken. The print will bleach more than you might expect though when it hits the fix. It's a pretty common practice to partially tone in selenium, partially bleach, refix and then tone more fully in selenium. It's pretty easy to get some funky yellowing with this method but....good luck.
I sometimes lightly bleach, sepia tone, then lightly rebleach and refix. The second bleaching strips away density from 'underneath' the sepia areas giving them a glow. If done carefully, it need not affect darker tones. Can be a very handy technique for certain subjects. Handy in the UK where sunlit areas might need a touch extra help (cos the sun if often low intensity if present at all). Have to be careful not to overdo it as the highlight can end up flat sepia with little density or contrast.
Bleaching re-introduces halides to the emulsion, which attach themseves to the silver. It is this that reacts to light and will slowly darken (print out) over time. Whether or not you then tone, you will still need to re-fix. This removes the halides and the image becomes stable again.
Can you tell I've be reading Tim Rudman's toning book?