Firefox 4 may be Intel-only on Macs, No PPC support if user number stays low.

Today, we got the news… Firefox 4 maybe be Intel only. PPC users should send some emails to Mozilla for consideration.

Mozilla will probably cut off Firefox’s PowerPC support past v3.6, according to the company’s director for the browser, Mike Beltzner. “I am gathering data on the number of PPC users we have, but the likely outcome is that we will not be supporting PPC [PowerPC] for Firefox 4,” he writes in a mailing list post. The root of the problem is said to be two new features in Firefox 4, beginning with out-of-process plugins, which can prevent the program as a whole from crashing when something like Flash becomes unstable. Also mentioned is a just-in-time JavaScript compiler, borrowing technology used in Chrome and Safari.

“I believe that Firefox 4 should be relatively faster and superior to previous versions — so to be better than Firefox 3.6, two of the significant mechanisms for performance improvement will not be available for PPC based computers, and so we are not planning on extending Firefox 4 support to those architectures,” Beltzner elaborates. A new PowerPC version of Firefox may still be developed, but if so, it may not even be called Firefox. The matter would be “a discussion with whomever wishes to publish those builds, as usual,” the director notes.

Firefox beta 4 was launched on Tuesday, and Mozilla says it was originally planning to freeze code for beta 5 on Friday. The update was to have included all of Firefox 4′s new features, but the company is reportedly having trouble, and so a fully-functional browser may have to wait for beta 6, which is scheduled to freeze on September 10th. Priorities may include performance, an improved interface and the Jetpack extensions framework, which should save add-on makers the trouble of constantly rebuilding code after Firefox upgrades.