And ZTF.
Possibly implement more multi-touch features for the trackpad.
ZTF is one thing you would need a new release for.
Plus with a bit of increased speed they could work out another release, it would obviously be smaller but probably a cleanup right before the dump of multi-touch OS in late 2010 or 2011 to match Windows 7.
10.6 Leopard II
I;d like to definitely see Fast OS switching with the advancement of Virtual Machines & bootcamp, i think it might be possible.
ZTF also would make a great addition.
Err... care to elaborate on what that "ZTF" thing is?
Or are you talking about the new ZFS filesystem from Sun Microsystems?
In case it's really the ZFS filesystem you're talking about, yes, it would need a whole new release to be implemented... But, AFAIK, it is far from being usable and dependable for a full operating system as of yet, so I'm betting you'd have to wait for at least 10.7 to see it implemented.
By the way, while I'm at it, I, too, think it is premature to end PowerPC support. One thing is killing Classic, which was *really* old when they did so (OS X was introduced in the early 2000's, so they started phasing out Classic at least 7 years ago); the other is to end support for an entire platform which, frankly, still has some life to it, besides having been fully discontinued only two years ago. My four-year-old Rev.A G5 iMac, clocked at a "measly" 1.8 GHz, still shows a very decent performance under Leopard (better than some new PCs running Vista, I could argue).
Also, in Leopard, Apple revamped already quite a lot of the system's underpinnings, so a new release focused mainly on security, stability and the obvious marketable features (like Tiger was, for instance) which maintained PPC support would seem obvious to me.