I would imagine that we'll see a reduction in the mid-day frequencies for exactly the reason you state.

Based on very casual observation of what people I know personally do for work, I would hypothesize that there's enough O&D traffic to keep the first three or four (359 lands in ORD at 9:30 Central, too late for a full work day but early enough for a day of meetings) frequencies and everything from 741 onward in the evening as is.

Plus I'll wager that 681 stays on the schedule since it's the "direct" DCA-NRT.