Mining is currently a level field for all, rich or poor. Even if and when Bitcoin becomes big enough to spawn specialized mining firms who develop proprietary ASICs for exclusive self-mining, you could still participate by means of a mining co-operative or a publicly traded company, or a partnership...
Except for ASICMiner, Avalon, BFL, (possibly KNCMiner, Bitfury in future). The companies that developed the first ASIC chips are doing
very well for themselves. The old adage remains true, in a Gold Rush only the shovel sellers make good.