Fees rise, transactions stall, businesses, suddenly providing poor user experience go into reverse adoption. Nothing happens for months and months since there is no room for growth and then the halving happens, miners switch off and our transaction volume drops to 1/3 or less because you can't compensate for slower blocks by increasing the transactions per block and difficulty moves out to 30 days and then longer as declining value causes more miners to switch off.

This is the scenario without 1MB blocks and some complicated fix slated for 2017 (an eternity in internet time). I'm confident a fix will be applied but it's now too late to avoid a lot of people being hurt. This is not an argument for bigger blocks any more, it's a straight-up prediction. Buckle up.