Yes, I believe the regular late pledge option is closed now. If you late pledge now, you'll be a late late pledge and may have to pay extra shipping/get your copy after everyone else does. You will still get all the extras/exclusives though.
This, as per their update in March that the PM was open for add-ons;
he deadline for submitting and paying for your pledge is April 4th, 2016. Don’t be late! If you fail to finalize your pledge by the deadline, your order will be shipped later and from the USA hub, incurring higher shipping costs and possible customs fees for international backers.