Theres loads of terrible sequels but reasons to be hopeful are
-they still do their characters to perfection (see video in OP)
-Christopher Guest seems to be about quality over quantity and has a very solid track record (rob reiner less so, but...)
-I dont believe they would do it if it was looking shit (whereas Dan Ackroyd by 2000 believed in UFOs and was long gone)
Interview with Derek Smalls from this summer
The bass player legend, played by Harry Shearer in the film This Is Spinal Tap, talks facial hair, courgettes and how to break out of a cocoon
www.theguardian.com