Re: Loyalty Issues
I agree with Scott; talk to your sensei, and see where it leads.
Maybe your "new" sensei will ask you "What do you hope to get out of learning under me?".
The answer you give might enlighten you both.
Regardless of the answer, there is no reason to abandon your former teacher. You could simply replace one of your regular classes with one of the new ones for an evaluation period.
And though I do not fully understand the first part of Szczepan's statement about Budo/Teacher/Student, I completely agree with his statement on aikido and federations; that being said, ranks do have to come from somewhere....or you could simply refuse to test ever again.