It is not presently clear as to whether the disabling of the megaprim constraints are intentional or not. We've got some third-hand information that Andrew Linden said that the change was not an intentional one, but Linden Lab have remained silent on the topic, so we've got no official answer on the matter.
A rolling update is starting at 7:30PM SLT (US Pacific time) today (Tuesday 13 May), which is rumored to reinstate the constraints among other 'crucial security fixes'. If so, the next couple days could represent your last chance to fabricate custom megaprims for a while.
The first round of updates is to approximately 150 regions, and starts in at 7:30PM SLT. The second round is in the morning (Wednesday) from 5AM - 9AM and will cover half of the grid's simulators.
The rest of the grid's simulators are being updated at 5AM - 9AM SLT Thursday.
We're still hoping to get an answer from Linden Lab, but we're not holding our collective breath on it, and neither should you. If you want to play it safe, grab a custom viewer (or roll your own) and make what you need sooner rather than later.
Users are reminded that the last information we have available is that megaprims are still not permitted for use on mainland simulators and are only allowable on private estates, where the covenant does not specify otherwise.
Update: Andrew Linden has said that the disabling of megaprim constraints was a bug, and is to be fixed. We assume that this particular rollout is that fix, though Linden Lab has yet to make any official statement or to respond to any queries.
Second Update: Linden Lab has responded to our queries.
