I wouldn't be surprised if Verizon announces another top of the line phone of either HTC, Moto, or LG tomorrow just to steal some thunder from Samsung and limit their supplier power. It's not in Verizon's best interest to have any one manufacturer dominate their phone sales, and if any manufactuer is in position to do it, that would be Samsung.
The other, more unsettling possibility might be announcing the end of unlimited data. I agree with PhiPsi32 that the vast majority of unlimited data users such as myself are currently no longer on a contract, and we're definitely the minority by a large margin. Since we're no longer on contract, this means that if Verizon ends unlimited data, we couldn't use it as an excuse to cancel the contract without paying the ETF so there's no real penalty for Verizon. Sure they'll lose some folks, but quite frankly the heavy users of unlimited data are probably the people they want to get rid of anyway. Heck, I actually wouldn't mind that so much as it would make my decision to get the GS4 a lot easier as I'd just take the subsidised price instead of debate whether it's worth the risk to pay full retail and possibly find out that unlimited data is going to end soon anyway.