First, you are asking multiple unrelated questions in one post.
Second, you are asking questions about the future that really cannot be answered.
Third, you are off-topic with questions about digital.
Fourth, you have random general questions.
"In the past, during the reign of film, camera manufacturers used to depend on Kodak-Fuji-Ilford-Agfa to come up with new films with new properties that gave the users new and improved experiences."
-Who else other than film manufacteres would manufacture new film?
What will the future of 35 mm SLR be?
-They will be few and far between. nobody really knows. Does that help?
Ever more in-camera software?
Digital, yes. Film, Doubtfully, but who knows?
Or will the SLR merge with the camcorder?
-Its allready doing that. Whether an SLR-like video/still camera style continues is comepletely dependant on the market and manufactures. Not likeley to go away anytime soon. Does it matter?
How will Nikon-Canon be able to get punters to buy a new camera every 3 year as they have done during the last decade?
-The same way any company does. Did you really need to ask that?
Is there a major paradigm shift in the 35 mm SLR future? -Yes. 42 of them.
What are your valued opinion?
-I like mustard better than ketchup.