Zach is technically correct in implying that the only way to get the Godzilla (or Brotherhood or GSXM or whatever) characters you want is to buy what they're offering now because if people don't buy Minimates, DST will stop making them, period. If they're not making Minimates anymore, there is exactly a 0% you will get the guy you want. If they keep making Minimates, that chance increases to 1% or 10% or 50%, based on the popularity of the character, Chuck's personal preferences, the airspeed of the migratory european swallow, etc. It's a sucker's bet to buy Minimates with the rationale of "I've bought every Marvel Minimate ever made, so I am owed a Banshee and Sunfire."
Buy them because you love them, not because you're hedging your bets against what they may or may not make in the future. Better to have loved and lost, and all that.