today Sony PlayStation 3 Hacker KaKaRoToKS has confirmed it is safe to update to PS3 Firmware 4.00 for those planning to use the exploit when it is released.
Below are some recent Tweets from him, as follows:
FYI, tested yesterday and the jailbreak still works on 4.0 so it's safe to upgrade (for those on 3.73)
Just got my progskeet today. Thanks uf6667 for sending it! It's so small!
Not much new to go on at the moment, but keep in mind the upcoming PlayStation 3 exploit will not enable PS3 backup managers such as multiMAN or Rogers as it does not include support for modifying Peek and Poke for lv1 and lv2 as outlined in the FAQ that was previously posted.