I dont think its a scam, they are not raising any ICO money, besides the community is growing mostly via communities,who are letting others know about the project. with over 3 million people already downloaded the app and over 100000 applied for running nodes when its ready.
you can read more here: https://www.cryptotapas.com/pi-network-is-gaining-traction-is-it-worth-mining/
also:  https://www.cryptotapas.com/should-i-mine-pi-network-coin/