I'm personally not buying that the Absolute Safe Capsule was meant to represent Porky, lots of objects are represented through Spirits, like the different Mario Kart vehicles, and the Absolute Safe Capsule is just another case of that imo. Like, if Porky himself had a Spirit, nobody would say he's represented twice, it's just something people cling to to try and explain something that likely doesn't have much of an explanation beyond a slip up or whatever. We're not always going to have an explanation for small things like these.
I definitely don't think it indicates that he'll be DLC though, I might have been able to entertain the thought had it been Sakurai who chose the DLC as he obviously has a soft spot for Mother (still wouldn't be likely at all, but at least not impossible), but as surprising as Nintendo may aim to be, I can't imagine why they would choose another Mother rep. At the very least with surprising 3rd party picks like Joker they get a ton of exposure, as much as I'd love it I really don't see where Nintendo's desire to include Porky would come from.