If there was an ulterior motive for the delay, I'd guess it's Waze.
If Lisk can be officially bought and sold on April 11, I've heard a lot of people express that they want to dump some Lisk for Waze since the first day of that ICO is April 12, and you get a 20% bonus on that day only.
If you support Lisk, this is probably a good thing. ICO investors might be less likely to dump their Lisk if they don't have a good reason for the funds.
NOTE: Yes, I have a Waze signature. I support both projects which is exactly why I've been seeing people talk about both projects. I follow both communities.
I had a feeling that this may have been the real reason too. Strange that Waves (Waze???) ICO starts on 12th just after the Lisk mainnet launch on 11th... and that too with a 20% bonus. Not insinuating anything but that is just bad timing.