So for the people who have the signature Visa and have not yet received a letter or have seen a notice on Chase.com about being transitioned to the MasterCard, you may still be in luck.

I also hadn't received either of the above 2 notices and I just canceled my card a few days ago by a secure message. The "senior representative", also by by secure message, verified that a MasterCard had not yet been generated for me. BTW, I'm still showing as platinum elite on ihg.com

Of course, the only conclusive proof will be, when I apply for the MasterCard, whether I receive the bonus again. I am in no hurry, so I will just wait until my next App-o-Rama and will report back here afterwards :-)