Facebook has already said it plans to bring its new Timeline profile to the Apple iPad, but has yet to give a launch date. The feature was supposed to arrive this month, but it was reportedly pushed back due to last minute bugs found during advanced testing, so now the update will arrive between mid-January and late January, according to 9to5Mac.
Facebook for iOS version 4.1 followed a few days later; Facebook probably had both versions ready at the same time, but had to wait for Apple's much more stringent app approval process. The update included access to Mobile Timeline on iPhone, and a note that iPad support was coming soon, but no further details.
Now Facebook for iOS version 4.2 has a rumored timeframe: it's just a few weeks away. I wouldn't be surprised if Facebook again has to wait on Apple for the iPad-specific update to go through, but if this rumor is correct, that's not the main cause for the delay.
As for Android, we know even less. Given that Facebook still hasn't supported Android tablets officially, the pessimist in me doubts we'll see Timeline for those devices anytime soon. The optimist would argue that Facebook was waiting for Timeline to launch before bringing its Android app to tablets as well, so as to avoid having to develop the profile twice.