Could it be that...?

There are more than a single Sith Lord?

Maul was Sidious's apprentice. We know that. But judging from the awesome power shown by Tyranus, maybe he is NOT Sidious's new active apprentice but rather one that was formed and came to 'maturity' as a master of the dark side? Sidious is obviously QUITE patient. He takes years to work on his 'plans'. Could it be that he turned MANY Jedis to the dark side and Tyranus is now powerful enough to train others himself? This way, Dark Jedis could surprise the shit out of Yoda and the few remaining 'good' Jedis in Episode 3? And in the end, Sidious exterminates them with the help of Anakin/Vader so they no longer are a threat to his reign. This would explain why Tyranius tried to make Obiwan join him. I remember reading that the Sith got extinct because of fights involving all of them... Maybe Sidious is so powerful and foreseeing that he formed more than one only eliminate them when he no longer needs them? Just a thought I had...

Go ahead 'Etienne Vachon', make my day...

No. Tyranus was Maul's replacement. As Count Dooku was already a powerful Jedi Master he didn't require much training. All Sidious needed to do was teach him the trick with the lightning and sew him some black clothes. You can see clearly that Palpatine's already got an eye on his replacement.

Yoda in PM: 'Always two there are: A Master and an apprentice' - Referring to the Sith.