I doubt it would make much difference, less than 1%.
Perhaps you missed the shiny graph, showing the 29%, nearly a third, of all potential iOS8 users who won't even install it, which says nothing of how many took the one-way trip of installing it and wished they hadn't.
This is the first release of iOS we've seen major pushback on resulting in fragmentation. No surprise that people would be resistant, considering the unpleasant experience going from 6 to 7 was, and how long that wreck took to stabilize. iOS8 has been even more troubled, and if people actually rely on their devices to function reliably, they're right to just keep what's working, working.