I honestly doubt that - the titles are still selling strong. Cancelling them wouldn't make much sense. The reason these rumours persist is because Loeb seems to have single-handedly been given the keys to the Ultimate universe (save Spidey). Bendis is doing his ULTIMATE ORIGIN which seems to be the last bit of the original Bendis/Millar/Quesada/Jemas hybrid that was the original ultiverse. Loeb is now ramping up his ULTIMATUM crossover which is supposed to be 'big', which is why he turned ULTIMATE POWER and ULTIMATES 3 both into set-ups for the crossover instead of them being stand-alone volumes, and he's taking over ULTIMATE FANTASTIC FOUR to help set up the crossover. Then there's the usual hyperbole of who may die.
What I would expect is a bit of a shake-up in team status quos and the universe itself, but I'd be surprised if they did anything like cancel the books because, as I say, they sell well, and ULTIMATE SPIDER-MAN is going nowhere.
Basically, Loeb 'finished' ULTIMATE POWER then did ULTIMATES 3, which are, perhaps, not just some of the worst Ultimate comics, but some of the worst comics ever - and the guy is, as I say, seemingly taking the Ultiverse in a 'new direction' and it's worrying because he's so ****ing dreadful.
Don't pick up the next issue if you don't like it. That's a waste of money. Comics you bought and enjoyed are never a waste of money. You paid for them, you enjoyed them, and you can re-read them and enjoy them again. Buying comics you know you don't like just to 'complete the run' (I know this pain) is the true waste of money - and your time.
Honestly - instead of ULTIMATES 3 #3, pick up another comic. If you like the medium of comics as much as you do, try other comics. I'm sure you'll like them.
Some suggestions: THE SPIRIT, FELL, ALL-STAR SUPERMAN, and HELLBOY. All fun reads. If you want any other suggestions or an expansion on these, you can either check the threads for them, or ask me or another poster who reads 'em. Plenty of good comics out there. Spend your money on the ones you enjoy, not the ones you used to.
It's good to have you posting, Pearl!