We never thought we'd see the day that Bond would die or that they'd reuse/recycle all the time in the world so how would you feel if DC played the villain in Bond 26 or if George Lazenby played Q ?
No thank you. That's just stunt casting, but worst of all it would encourage the "code name" theory crowd.
I agree with Number24, and add that it would distract attention away from whoever is the new Bond.
Again, NTTD was the 25th Bond and acted as a nice victory lap for the Bond series to that point. I really think they're going to completely start fresh with Bond26 and try and not reference the prior films at all.
I'm generally opposed to the idea but would make one exception: I wouldn't mind seeing Dalton play a villain. Three reasons why: (1) He'd be very good at it. (2) He deserves to appear in more than two Bond films. (3) It's a new continuity, so anything goes.
I think new movies will reference the old movies indirectly in the sense that we may see places, objects, lines and situations that remind us of the old movies. Maybe we'll see aircraft like Little Nellie, Bahamas used as a location, hear "We have a saying too, and you're full of it" again etc.