The blocksize topic correlates directly with the current 7 transaction per second (TPS) ceiling Bitcoin has that was recently brought to light before US Congressional Testimony. https://en.bitcoin.it/wiki/Scalability describes the 7 TPS ceilings under "Current bottlenecks". Ignore block framing data fields, the 7 TPS limit implies that ~4200 transaction (10607) with each being ~238 bytes in size fitting nicely into the 1MB block brown bag. A careful examination of the top of blockchain-dot-info will indicate the real world is a little more complex, and the 7 TPS ceiling is extremely optimistic, most transactions will be significantly larger than 238 bytes size! My mining Payouts alone are ~4K in size.
The tweaking of the blocksize a very hot/political topic. Remember the March 12, 2013 Bitcoin forked Blockchain issue??? (http://bitcoin.org/en/alert/2013-03-11-chain-fork) It is too early for me to tell what the trade space pros & cons [system's engineering truth concerning the trade space analysis of alternative (AoA) results for backward compatibility, scalability, security, sustained decentralization... measures of effectiveness (MOE) and measures of performance (MOP)] is for increasing the current 1MB block size in the Blockchain.
Ignoring state politics, in the end, the dynamics between stability of developer solutions, hardware engine solutions, miners and pools will ultimately determine the block size(s) supported in the future.
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