As have been mentioned above, a cadetship would probably become the preferred way most people enter the airlines in the future. Just like what Asia have been doing in the last 20 or 30 years ... .This of course will be highly competitive and if you don't get a cadetship, and you're determine to fly for a career, then of course you'll have to go through GA.
The majority of people who start out in GA are working their way to get an airline job and many along the way fall away by the wayside. Those who are determined and persist will make it. I believe luck sometimes has a lot to do with whether you make it or not. I'm sure a few here would who have made it in to an airline from GA would have a 'lucky break' story to tell.