I think you're reading more into his comment than he intended. The first tweet,
Last known state for rocket boost stage is 360 m/s,
Mach 1.1, 8.5 km altitude and roll rate close to zero
(v important!)
Was a very upbeat message in the context of their previous attempts.
This rocket was only doing 360 m/s, but importantly, wasn't rolling at all -- Their last 'test' failed when the rocket started rolling at a very high rate of speed and they lost engine power.
Musk was then asked:
if anything could go better, what would it be?
To which he replied:
Rocket boost stage reaching 0 m/s in one piece :)
Will know soon. Odds not high.
The first line is just a joke that the test would go better if the rocket got to the surface in 1 piece. I think his 'odds not high' statement is just to dampen excitement a bit, since they went into this with a ~40% chance of success for the landing stage.
This rocket was only doing 360 m/s, but importantly, wasn't rolling at all -- Their last 'test' failed when the rocket started rolling at a very high rate of speed and they lost engine power.
Musk was then asked:
To which he replied: The first line is just a joke that the test would go better if the rocket got to the surface in 1 piece. I think his 'odds not high' statement is just to dampen excitement a bit, since they went into this with a ~40% chance of success for the landing stage.