I wouldn't be surprised to see them move to an 8pm show on Saturday after Andrew leaves. But if they're canceling the last few late shows on Saturday night, I don't know that they'd also want to potentially inconvenience a second group of ticketholders by changing the performance time for them as well. Yes, there might be little harm done -- making a show later is easier than making it earlier. But as odd as it might be for 3 or 4 weeks (unsure how many they are canceling), they might just decide to leave it alone if they have a lot of tickets sold for the earlier show already.
As for "energy", I agree that the Saturday 10pm show had an awesome vibe. But energy and vibe isn't going to keep the show running. If they've decided that they should only play seven, it behooves them to pick the show to cancel that is selling the most poorly.
Also, I don't think we can underestimate the exhaustion factor. As it is, playing two evening shows within five hours was pretty unusual and -- I can only imagine -- draining for all concerned. Yes, NPH did it. Others might be able to do it too. But like NPH, Andrew doesn't have an understudy. If they decided that 8 was too many and they wanted to do seven that also wouldn't be unduly taxing, canceling one of those Saturday night shows helps a lot to make that weekend schedule more bearable -- more so, in my opinion, than the Sunday matinee.
"No matter how much you want the part, never let 'em see you sweat." -- Old Dry Idea commercial