Yes developing and 3rd world countries will be the places where Bitcoin will really take off first.
The developed countries however are the ones who mostly build the infrastructure (exchanges, wallets, merchants, markets, most fo the startups).
Latin and South America, South east Asia, parts of Eastern Europe are the places where Bitcoin will be adopted in a bigger scale first imo in terms of daily usage.
Regarding the financial, speculative aspect of Bitcoin it will be USA, China,UK, the developed countries in general to adopt Bitcoin first.