The situation has probably worsened. Opera lost out-of-the-box APNG support with the switch to Webkit. Firefox has lost market share to Chrome on the desktop,

The situation has probably worsened. Opera lost out-of-the-box APNG support with the switch to Webkit. Firefox has lost market share to Chrome on the desktop, and were never big in the (still growing) mobile market. There is a simple Chrome extension that adds APNG support, but anything that is not installed by default is unlikely to be used by most users. 90% of Chrome users don't even install an ad blocker!