With all these suggestions of Clint Eastwood as an old Bruce Wayne, you're forgetting 2 important things:
1) Eastwood has pretty much retired from acting - he only directs movies now.
2) Eastwood does not star in other studio's movies anymore. He hasn't done for decades. He's not like the traditional Hollywood actor who takes whatever job he gets from different studios. He only makes his OWN movies using his own company, Malpaso, and maybe occasionally stars in them. His films are usually about his own subject interests, and quite frankly, I don't think Batman is one of them.