I don't have a problem with triple threat matches as long as there's a purpose. Like Orton/Triple H/Cena at WrestleMania XXIV (one of my favorite triple threats). Pretty sure the plan was for Cena to face Triple H that year before he got hurt, then Orton took his place. Then Cena came back earlier than expected, so they had to find a way to keep Triple H in the title match while also accommodating Cena. The way they did it made sense and ensured that nobody got left out. It also gave us a match we've never seen before.
They knew that Rhea/Bianca was a big-time match and they wanted to build it up as much as they could before it happened. The fact that they're openly acknowledging it lets me know they're going to get to it, whether it's SummerSlam or next year's Mania. At the same time, Iyo has been in the mix for a while and she's hot right now, so they wanted to capitalize on it. It probably won't be the main event, but it will still be one of the best matches on the card.
Punk/Rollins/Reigns may or may not happen. If it does, they're going to need to put a stipulation on it, like the winner gets added to the WWE Championship match the next night. If it doesn't, they'll have Rollins/Reigns and Punk will probably get into the WWE Championship match some other way. A triple threat with no prize is weird, and I doubt they go another year without putting Punk in the main event, so this is the only way to make it happen.