Can you imagine a brokerage in the US being able to say that the underlying is 'designed to increase in value' or that it's value 'decreases occasionally'? They couldn't because it would be illegal.
Bitcoin does not represent the assets of any enterprise. Currencies have their value pegged (at some point) by a soverign which Bitcoin doesn't have. Bitcoin is designed to float (which means rise to the top) amongst other currencies. That is axiomatic of the design of cryptocurrency, not merely a prediction.
"float" doesn't necessarily mean "float to the top" and limited supply is not a feature of cryptocurrency. It's a feature of most cryptocurrencies currently in existance.
Also, it was not a "design goal" of bitcoin to keep increasing in value. I'm sure satoshi had that hope, but it's not built into the system because "value" isn't built into the system. Scarcity is built-in, "value" is given by the users, not by technology.
It doesn't suit mtGox well to try to calm the panic by speculating on the price going up. It's just not their job and to do so is equally unprofessional as not getting help with fixing the engine or fixing it in time which might even have prevented the panic in the first place.
I absolutely understand your positions. I simply don't agree with them. That's my opinion. I am not a currency professional and neither are the folks at Mt Gox.