Usually I wouldn't post just a rumour, but as there's photos of the new Canon MT26EX I don't think there's any doubt. It's about time they replaced it. My MT24EX expired a few years back and I got it back from the Canon official service centre as too uneconomical to repair. Given how many problems others have had with the MT24EX I was never tempted to buy another one as it should have been due for replacement.
The photos appear to show it similar to the original, just with RT. I hope it's got weather sealing like the Canon 600EX RT. I won't be in a hurry to get it as I bet it will cost an arm and a leg, and the Yongnuo YN24EX is proving just as good as the MT24EX at a fraction of the price. I've thought most flashguns were grossly overpriced since the first dedicated TTL units started appearing in the 1980s. You've got some pretty standard non-expensive electronics in a cheap plastic case, and you pay a fortune just because the manufacturers keep the protocol of the flash/camera interface secret. Maybe when the first dedicated TTL units came out they could claim they were recouping development costs, but well over 30 years later I think that excuse no longer washes. Rant over, but I do wish the manufacturers would charge reasonable prices for what is in reality standard electronic technology that hasn't changed much in the last 40 years.