The maximum supply of Base Set and Transcendent Set crates are 400,000 each. No more than this amount can be minted, ever.
The only way to buy crates at the moment is from another Serran in trading. Be aware though that any trades discussed in trading are executed at your own risk. Peer-to-peer trades are risky and we really don't recommend doing p2p trading. Especially p2p trades without a middleman are highly risky.
Please see Tips to trade crates safely for tips on trading safely.
Unfortunately, there is a bug with OpenSea meaning that crates cannot be traded, please get in touch with OpenSea if you would like to be able to trade Synergy of Serra crates on OpenSea.
We have yet to release two Factions, there will be more expansion packs in the future! However, a release date for any new expansion set is yet to be announced.