the thing is ... if you upgrade the transaction speed from 4 to 40 ... much people adopt this because it cost nothing compared to other service.
How many transaction are completed in Paypal, OKCoin, Alipay, etcs ... ?
i don't completely agree with the way you say this. the transaction speed is high enough, it is almost immediate. the slow part is the confirmation part which will take some time and right now since there is no longer any spam attack it is less than 10 minutes for normal fees.
also people who want to adopt bitcoin don't see this issue at first so that is not the thing that prevents adoption.