iOS is Apple's new focus and replacement for OSX. I believe OSX 10.7 will be the last version of OSX as iOS will morph to live on any size system or device. Time will tell but I believe this to be true. We'll see what happens when AppleTV is released - maybe real Apple televisions will be announced with AppleTV devices.
I very much doubt iOS will replace OSX. This would mean walled gardened Apple computers.. which would be the kiss of death. If SJ emails is to be believed, he already said Apple have no plans to lockdown and restrict Mac software.
Personally, I think iOS and mobile devices have taken up too much of Apple's resources and it won't be until next year's WWDC that we'll see 10.7. iLife has obviously suffered - Apple have been too busy with adding iLife software to iPhones and Pads.
If Apple have indeed given up on OSX - then its a sad day. I feel sorry for all those new switchers.