I have talked to chase about this twice, and received a letter yesterday.
The letter was simply how my old card will credit to my new account, and to contact UA to get my new 8 character MP number (if I don't have it already).
Chase assured me that my signature card, and its benefits would be grandfathered in. I personally have zero interest in an explorer card, and would ditch the whole thing if I had to give up the signature perks. As far as new cards with new mp numbers on them go, I was told no new cards will be issued until old cards expire - so we will see. Plus, who wants a new card anyway....it won't have a tulip
