Well that would depend if all governments would collectively state their support. Demand would definitely explode but i don't expect anything like a x100 pump. I think btc is over that kind of movement already.
Not really a x100 pump but atleast wr can see some pump for the price of bitcoins as it will really make a better increment in the amount of investors. Legalising bitcoins is been a main issue since more than an year but no legal action has yet been taken so it is really much hard ti predict anything about the legalising future of bitcoins.
Also i think that bitcoins can only gain some legalising importance if all the governments globally take a final decision together about the decentralised currencies. I can see that Iran has already legalised bitcoins and you can see the price for bitcoins there. They are sky reaching.