Don't really think that's going to happen. Pork is one of the cheapest meats you can raise.

Just the spore costs to produce a lb of mushrooms can rival the total cost to raise a lb of pork (commercial pork can be as cheap as $64/CWT carcass weight - so $0.64/lb. Mushroom spore can be as high as $1.00 in spore costs to generate 1lb of mushroom). Processing the meat will raise costs, but it's hardly like mushrooms have low care/processing costs (If you don't know, they often require clean room levels of care to ensure proper spores without contamination).

There's a reason white mushrooms (unsliced) goes for $4.49/lb at my local Kroger, and the boneless pork goes for $1.99/lb.

I don't see this ever being cheaper.