I don't necessarily think losing the V8 in the old model will make the older models more desirable. Ford pulled off the twin turbo V6 and by all accounts it is a very durable engine. The only complaints I've heard from friends who own them is that real world economy is less than expected. Unless Toyota has issues with the new motor, and being Toyota I would be surprised they didn't vet the heck out of this thing before getting it into the market, I think it will be fine.
We have a Ram 1500 with the 5.7 mild hybrid that is less than a year old. Fabulous truck. Was going to buy the Tundra until we drove the Ram. No comparison in terms of ride quality or interior fitments, except that Toyota has the long term reliability/durability reputation. This new Tundra looks much more modern, although I think the Ram still looks better and less awkward. But if they get the build quality right, and again it is Toyota so I would doubt there will be issues, this will be a huge hit for Toyota.
