Really, wow! Will there be a qualifying round to give associates an opportunity to play in the World Cup? I think it is not a very good thing to do if you want to grow the size of the cricketing world.
I think its a bit of a catch 22. The current world cup I think is 44 days which in itself is much longer than the football (or soccer depending on where you live) world cup at 32 days, and that is a truly global game with 32 teams playing (and more than a 100 others wishing they were a part of it). In cricket it is essentially always been 8 for a long time, and in general most likely those 8 will go through to the quarters (WI might be an exception this time on form).
I think I read it somewhere that they could have had 4 groups of 4 (ie add 2 more teams) and still had a shorter world cup if structured correctly (the 2007 one was longer at 49 days). One of the reasons it has been structured as 2 x 7 is to avoid the 2007 situation (which was 4 groups) where India and Pakistan failed to make it past the group stages. In the next cup presumably that will mean 2 pools x 5 nations each - almost kinda beats the point. Might as well start off with quarters and the top 8 and be done with it
From the point of growing the game I think the 16 teams and the 4 x 4 format was a good idea. The problem is probably something like 80 per cent (likely more) of the viewing audience and the revenue comes from the subcontinent (majority from India), so they are kind of forced to ensure those nations get through to the elimination stages at least.