As is mentioned in this Reddit post, the PHP-FIG group has moved a new autoloader structure proposal into "Draft" status, making it past the initial proposal (Entrance Vote) level as PSR-4.
This new autoloader has been in the works for a while, and is meant to be a modern autoloader that reflects the changes in the PHP landscape since PSR-0 was originally put together. Yesterday it passed the Entrance Vote, which means its now a formally worked and supported by the FIG.
While PSR-0 is new to many, its been around for years - since before Composer was really a thing - and PEAR/SF1/ZF1 were the prominent sources of distributed code. Now that so many are building components with Composer and using PSR-0 (yay) it's about time a new standard took care of a few hangovers from the PEAR/Zend style.
The newly proposed autoloader gets rid of some of the allowances that PSR-0 included like proper namespace support (no more underscores) and a reduction in the required folder structure to make it work. The Composer project is also a part of these discussions and are on board with making these proposed changes in the project's autoload handling.
We'd love to get constructive feedback on PSR-4. Post stuff up here, on the mailing list, get in #phpfig on freenode, whatever, just get involved. That doesn't mean everything will be implemented, but there is more chance of the standard containing your feedback if you make it - so post something.