Triple heel turn could happen because there are rumors of the return of the
NWO big 3.
The NWO versus the Shield would probably make the Shield heels.
Even if that's true, it won't be Hogan, Hall & Nash taking on the Shield as they'd never be medically cleared. Hogan wasn't cleared when he returned to the company a few years ago; WWE would hardly even allow Hogan to do anything physical. Nash recently underwent something like the 25th knee surgery of his life and Hall either has hip replacements or is in need of them. Hogan just turned 65 years old, Nash recently turned 59 and Hall will be 60 in October so...yeah, not exactly something that'd be anything resembling an actual match.
The only thing I could see would be Big Three of the nWo passing the torch and the nWo name to some other group of young guys but that has almost no chance of taking place because it's too much of a gamble. Truth be told, if the nWo was gonna pass the torch to any group of three guys, it'd probably be the Shield.
As for the cash in attempt and crowd reaction, the crowd exploded once the Shield's music hit and Ambrose & Rollins came out wearing the riot gear. As for why Strowman was waiting around, it was just a brief screw up in timing but I'm not gonna nitpick at it. Strowman could've kept beating up on Reigns after he handed off the briefcase, but the match wouldn't have started as refs don't start matches when one guy is getting his ass handed to him before the bell officially rings.
I think what will happen is that Strowman will put his cash in plans on the backburner for a bit for as long as the Shield remains together. Every rumor and report I've read suggests that Ambrose is slated for a heel turn at some point in the relatively near future, as that was the plan for his team with Rollins before he was hurt so I have a feeling the turn is legitimately coming. As for Reigns, I think there's a chance that WWE has continued to trap us in the unending waiting game that is Reigns vs. Lesnar; don't be at all surprised if the plan is for Brock Lesnar to stay gone for the rest of the year and to invoke his rematch clause for WrestleMania next year. The Royal Rumble winner will be another wrestler from SmackDown and by then, it's
POSSIBLE, I suppose, that Lesnar will be UFC Heavyweight Champion and if that's the case, then Vince will want to do some sort of promotional bit where Lesnar pops up on Raw the night after the Rumble, is UFC Heavyweight Champion and invokes his rematch for WrestleMania.
IF that is indeed the plan, then everything Roman Reigns does, every feud he has and opponent he faces is just a holding pattern until this fucking thing with Brock Lesnar is finally and completely finished.