It won't make much of a dent at all in total traffic. More than a drop in a bucket, to be sure. More like a cup out of a large bucket.
I would guess that traffic levels in the EDIG board are way down from previous levels as evidenced by its Top Boards score tanking lately. In fact, looking at the daily posts for that board, it looks like its score is going to seriously plummet soon. The scores take the last 72 hours' posting activity into account (which is why the numbers change so often) and its 3rd-highest activity day was 2 days ago. When that day rolls out of the calculation and is replaced by yesterday's, today's, and tomorrow's lower traffic there, the score's coming way down.
Total posting volume yesterday was down 5% from the day before and down 10% from a week ago.
Pageviews were up 2% from the day before and up about 3% from a week ago. We're still hovering about 5-10% below the alltime record for daily pageviews, set a month ago today.
Really, that board could theoretically be shut down right now and it'd be no more than a small dip in the traffic chart.
That really blows out of the water the oft-stated "fact" that if the EDIG folks just abandoned iHub, it'd kill the site. Your workload of a few days ago would get cut by 90%, but not the site's total traffic. That board is seriously dwarfed by the #1 and #2 boards.
Edit: I looked at the formula for Top Boards calculations, and would estimate that that board's score is going to lose about 100 points this weekend if the current trend continues. Also, it looks like that board's traffic accounts for between 5 and 6% of the site's total traffic.