If you’re using 64-bit Windows 7 system and eagerly waiting for 64-bit version of Firefox for Windows it is unlikely to available for you in future. FYI since some time for now Mozilla already offering Firefox nightly builds for 64-bit Windows but they never reached stable version and won’t be in future as Mozilla decided to put a stop to development of 64-bit Firefox nightly builds for Windows due to the following reasons.

No 64-bit version of Firefox for Windows

  • Many plugins are not available in 64-bit versions, The plugins that are available don’t work correctly in Firefox
  • Crashes submitted by 64-bit users are currently not high priority because we are working on other things.
  • This is frustrating for users because they feel (and are!) second-class.
  • It is also frustrating for stability team triage because crash-stats does not easily distinguish between 32-bit and 64-bit builds  in the topcrash lists and other reports. We basically ignore a set of nightly "topcrashes" because they are 64-bit only. (See bug 811051).

Its true that 64-bit Firefox version can take advantage of memory address space on 64-bit Windows system to offer more performance and security than on 32-bit.  But lack of plugins is the primary reason and Mozilla also not able to allocate time for fixing crashes encountered for 64-bit version considered as second one -put this way high priority  has been set for Android and Firefox OS now-.

At present you need to satisfy with Opera and Internet Explorer as they’re natively offered in 64-bit versions for Windows.

Waterfox and Palemoon two 64-bit variant Firefox versions to try out

You can try unofficial 64-bit variants of Firefox like Waterfox and Palemoon on your systems. Former is optimized to run more faster on Windows and delivers automatic updates where latter pushes updates slowly.

Does Mozilla also kills plan of offering Stub installer for Firefox?

With keeping 64-bit Firefox version in mind (?) Mozilla planned to offer stub installer for Windows which negates 32 & 64-bit download confusion. Now what happens to stub installer which not yet officially available for Firefox stable version? Mozilla needs to answer this. We don’t need to be surprised if Mozilla sticks to web installer also.