I don't see it as an issue of chance rather as an issue of timing.

Consider that in a poker game, people will change the world state on the order of seconds and minutes and not milliseconds. The world state in your game example means changing a card, folding, bluffing, ante-ing, hitting, etc... none of these actions are very fast in terms of the SQL database application and thus there is very little to no chance of concurrent queries being inconsistent.

Hence, In My Humble (and admittedly ignorant) opinion, while you may feel that this is leaving things to chance, in actuality even 100 function calls to a MySQL engine in a second (representing 100 functions, representing 100 tables) is child's play compared to what MySQL can do.