Looks like Pixmac is going to shut down at last, according to this e-mail:
Dear Pixmac contributors,
Pixmac is now part of the Pond5 family. Pond5 is the world's most vibrant marketplace for creativity, with the highest royalty rates for artists in the industry. At Pond5, youll be able to set your own prices, and there are no exclusivity restrictions.
As a result, the Pixmac site will be shutting down and merging into Pond5 in early September. In anticipation of this, Pixmac will no longer be accepting new uploads.
Content Transfer to Pond5
Your content will be automatically moved to Pond5 by September 31, 2015.
Pond5 Terms & Conditions
The Pond5 Terms and Conditions can be reviewed here.
Payment
Outstanding royalties will be paid by October 1, 2015. To request payment before that date, please log into your account and fill out your payout data here. Any unpaid royalties earned after that date will be transferred to Pond5. You will then be paid on Pond5s payout schedule.