His selection depends whether Australia wants to take another hit and miss bowler into a Test. For me, Siddle's a good bowler when you're losing a series as he might just bring that spark that you need - otherwise I think he's too much of a risk. I'd rather Copeland's steadiness.
Sadly I'm pretty sure the selectors will pick Siddle. If it is the case then I just hope he gets the consistency into his game as we can't keep going down this path of having 2 inconsistent bowlers in the side with a new spinner.