I'm still a little unsure of why they are holding back on the Userland exploit, except that since it is the easiest one to administer they may be waiting to use it as a way to automate the other exploits.
For example, if the Spirit jailbreak (I have no clue how it works) can be executed with no computer, then they could have you download an app into userland, like say blackra1n, that would exploit from the device itself. Granted, the exploits also sound like they are independent, but they may be waiting because it's the EASIEST way right now.
My guess is they just want to communicate with each other to make sure they don't release two exploits at the same time unnecessarily. So they'll probably look at the likely hood of Apple patching any of the exploits they have and make a decision to only show one card at a time.
I'm excited though! Even though I already have a jailbroken 3G running 3.1.
As for LockInfo working on 4.0... If the firmware change isn't too great it should be compatible. Most existing API's don't change so much. As soon as MobileSubstrate and Preferences Injector are ported LockInfo may just need to be recompiled. Only time will tell. Ashman seems like the kind of guy who'd be on top of that if he could get ahold of the firmware.