Maybe it's just an excuse to introduce a new character, like Sly did in rocky 5 (well he also came back for a rocky 6, but still)
Anyway, I would 100 times rather watch a rambo 12 with a 90 yo Sly than a Terminator w/o Arnold.
Sly made some good stuff with the expandable, I'm confident rambo 5 will be fun to watch, even if it doesn't reach the class of rambo 1.