We have at least 2 more years before the block size limit actually starts mattering on a significant scale:
https://blockchain.info/charts/avg-block-size?timespan=all&showDataPoints=false&daysAverageString=1The moving average for this years block size has been about 0.4 - 0.44 MBs.
So Gavin couldn't negotiate with the core devs any longer and had to get his coin out ASAP because... why?
The fact that he is backed by a throng of finance industry CEOs diminishes merit from his arguments. We don't care what the already-rich think. Bitcoin isn't for them.
Because big boys are asking so and won't wait any longer for obvious reasons. The limit also limit these companies to mass marketeer their products.