I think this is a case of you both being right but it is anybody's guess -- well maybe Robert Milton knows for sure -- when the Royal Bank connection will be broken. Unlike Amex, Royal is a secured creditor of Cdn: it is the company's primary bank (as CIBC is AC's). It has a vested interest in the restructuring, and AC has a vested interest in keeping Royal reasonably happy.
That said, when Cdn metal does go, it is likely Royal will phase out its Cdn+ Visa card but there should be plenty of notice and if it is mid-way through a membership year, your annual fee would likely be pro-rated and refunded, or credited to a new Royal Visa which will be made attractive to keep your business.
AC of course does have agreements with exclusivity with CIBC (Visa) and Citibank (Diners|enRoute). A way to include Royal might come if AC spins Aeroplan off as a subsidiary company (as rumours have suggested) permitting renegotiation of credit card tie-ins.
The Cdn+ Visa remains competitive since you get the annual renewal bonus of 2.5K and first flight bonus of 2K. You are likely to just get a one-time 5K sign-up bonus with Diners of CIBC Visa, I hold off on switching cards until the dust has settled.
(An interesting side bar: Royal Visa is the official credit card for British Airways, so we may see that program brought to Canada if the Cdn+ card is phased out, and BA gets agressive in the market here.)