Pharo is a fork of Squeak, loosely along the lines of "let's rip out and replace as much old cruft as we can" vs. "let's maintain backwards compatibility where reasonably possible", respectively.
The big news here, however, is the new VM and image format, and since Pharo and Squeak have never diverged in that area, it's likely that Pharo will benefit from these improvements as well.
It will indeed. The current plan (subject to change) is that Pharo 5 will ship as Pharo 4 + Spur (32 bit), then Pharo 5.1 will be Pharo 4 + Spur (64 bit), and then normal releases will resume. But as I said, that's just the current plan, and so much has landed on the 5.0 branch already that I'm a bit dubious they'll stick to that.
The big news here, however, is the new VM and image format, and since Pharo and Squeak have never diverged in that area, it's likely that Pharo will benefit from these improvements as well.